Seoul, South Korea (CNN) A North Korean senior intelligence officer has become the highest-ranking military official to defect to South Korea, a government source confirmed to CNN. 
 
 The defector was a senior colonel with the North Korean Reconnaissance General Bureau, which is in charge of espionage operations against South Korea, according to South Korean Defense Ministry spokesman Moon Sang-gyun and Unification Ministry spokesman Jeong Joon-hee. 
 
 North Korea's Reconnaissance General Bureau is a powerful body, responsible for clandestine operations, including espionage against foreign countries and cyberwarfare operations. 
 
 Speaking in separate news conferences Monday, the ministry spokesmen confirmed that reports from South Korea's semiofficial Yonhap News Agency on the defection were accurate but said they could give no further details. The colonel had defected last year, according to Yonhap , but CNN cannot independently confirm this. 
 
 The announcement of the high-level defection followed news last week that 13 North Korean nationals who had been working at a Pyongyang-owned restaurant had defected to South Korea, officials in Seoul announced. The restaurant workers, 12 women and a man, said they had defected after "feeling pressure from North Korean authorities" to send foreign currency back to their homeland, South Korean officials said. A Chinese foreign ministry spokesman confirmed that 13 North Koreans who worked in a Pyongyang-owned restaurant in China left the country legally on April 6. 
 
 On Tuesday, North Korea threatened defectors in a commentary published in its state-run propaganda site Uriminzokkiri, calling them "gangsters little short of thrusting daggers into the lifeline of all families in the DPRK." 
 
 Many defectors have expressed concern for their family members who remain in North Korea as the regime is said to practice guilt by association -- in which people closest to the individual are punished. 
 
 The North Korean commentary threatened those who defected to South Korea of "pre-emptive, consecutive attack on them in a more deadly and severe punishment without any warning and prior notice." 
 
 Fleeing brutality 
 
 JUST WATCHED North Korean defectors struggle to fit in Replay More Videos ... MUST WATCH North Korean defectors struggle to fit in 02:18 
 
 All North Korean defectors are interviewed by South Korean intelligence services for information about life across the border. 
 
 It is expected the latest, high-profile defector could prove a rich trove of knowledge about the workings of North Korean leader Kim Jong Un's secretive regime. 
 
 Tens of thousands of North Koreans have fled poverty and repression in the isolated North in recent decades, but defections of senior officials are less common. In the first quarter of 2016, North Korean defections to South Korea rose by 17.5 percent compared with the previous year. Between January to March, 342 North Koreans fled to the South, Yonhap reported. 
 
 Last year, a high-level defector told CNN that Kim was taking an increasingly brutal approach to the elite, executing them when they fell out of favor. 
 
 The hard line on aides and officials was eroding Kim's fragile support base, the defector said, in comments CNN was unable to confirm independently because of the challenges of verifying information inside North Korea, one of the world's most closed societies. 
 
 Tensions have ratcheted up on the divided Korean Peninsula this year as Pyongyang has made a series of assertions about developments in its military capability. ||||| A man watches a TV news program showing file footage of North Korean leader Kim Jong Un at Seoul Railway Station in Seoul, South Korea, Monday, April 11, 2016. A colonel from North Korea's military spy... (Associated Press) 
 
 A man watches a TV news program showing file footage of North Korean leader Kim Jong Un at Seoul Railway Station in Seoul, South Korea, Monday, April 11, 2016. A colonel from North Korea's military spy agency fled to South Korea last year in a rare senior-level defection, Seoul officials said Monday.... (Associated Press) 
 
 A man watches a TV news program showing file footage of North Korean leader Kim Jong Un at Seoul Railway Station in Seoul, South Korea, Monday, April 11, 2016. A colonel from North Korea's military spy agency fled to South Korea last year in a rare senior-level defection, Seoul officials said Monday.... (Associated Press) A man watches a TV news program showing file footage of North Korean leader Kim Jong Un at Seoul Railway Station in Seoul, South Korea, Monday, April 11, 2016. A colonel from North Korea's military spy... (Associated Press) 
 
 SEOUL, South Korea (AP) — A colonel from North Korea's military spy agency fled to South Korea last year in an unusual case of a senior-level defection, Seoul officials said Monday. 
 
 The announcement came three days after Seoul revealed that 13 North Koreans working at the same restaurant in a foreign country had defected to the South. It was the largest group defection since Kim Jong Un, North Korea's young leader, took power in late 2011. South Korean media reported that the restaurant is located in the eastern Chinese city of Ningbo. 
 
 Defections are a bitter source of contention between the rival Koreas, and Seoul doesn't always make the high-profile cases public. Liberal lawmakers and media outlets have linked the recent defection announcements to what they say is an attempt by the conservative government of South Korean President Park Geun-hye to muster anti-Pyongyang votes ahead of this week's parliamentary elections. The government denied this. 
 
 The colonel who defected worked for the North Korean military's General Reconnaissance Bureau before fleeing to South Korea, according to Seoul's Defense and Unification ministries. Both ministries refused to provide further details, including a motive for the defection. 
 
 The Unification Ministry said that a North Korean diplomat based in Africa separately defected to South Korea last year. It didn't elaborate. 
 
 The reconnaissance agency was believed to be behind two deadly attacks blamed on Pyongyang that killed 50 South Koreans in 2010. 
 
 There have been occasional reports of lower-level North Korean soldiers defecting, but it is unusual for a colonel to flee to the South. 
 
 The highest-level North Korean who took asylum in South Korea is Hwang Jang-yop, a senior ruling Workers' Party official who once tutored Kim's late dictator father, Kim Jong Il. Hwang's 1997 defection was hailed by many South Koreans as an intelligence bonanza and a clear sign that the North's political system was inferior to the South's. Hwang died in 2010. 
 
 More than 29,000 North Koreans have defected to South Korea since the end of the 1950-53 Korean War, according to South Korean government records. Many defectors have testified that they wanted to avoid the North's harsh political system and poverty. Pyongyang usually accuses Seoul of enticing North Korean citizens to defect. 
 
 The announcement on the defections comes as the two Koreas trade threats amid Pyongyang's anger over annual South Korean-U.S. military drills that North Korea calls a rehearsal for an invasion. The North has fired a slew of missiles and artillery shells into the sea in an apparent protest against the drills. 
 
 South Korean officials said they disclosed the restaurant workers' group defection because it was an unusual case and happened after tough U.N. sanctions were imposed over Pyongyang's nuclear test and rocket launch this year. The officials said they confirmed the two individual defections in response to news reports on them. ||||| (This April 11 story has been refiled to correct spelling of ‘Korean’ in final paragraph) 
 
 North Korea's surveillance cameras sit on the top of a steel tower to overlook the south, near the truce village of Panmunjom, South Korea, March 30, 2016. REUTERS/Kim Hong-Ji 
 
 By Jack Kim and Ben Blanchard 
 
 SEOUL/BEIJING (Reuters) - Two senior North Korean officials, including an army colonel specializing in espionage against the South, defected to South Korea last year, the Seoul government said on Monday. 
 
 News of the defections followed a South Korean announcement on Friday that 13 workers at a restaurant run by the North in an unidentified country had defected, a case it described as unprecedented, arriving in the South a day earlier. 
 
 South Korea did not say where the 13 had worked. China said on Monday that 13 North Koreans had been there and had left lawfully. It did not say if they were the same group. 
 
 The South’s Unification and Defence Ministries said on Monday a North Korean army colonel defected last year and had been granted political asylum. He had worked in the secretive General Reconnaissance Bureau, which is focused on espionage activities against the South. 
 
 South Korea’s Unification Ministry, which handles North Korea issues, also said that a senior diplomat who was posted in an African country had defected to the South last year with his family. 
 
 The defection of a high-ranking officer in the General Reconnaissance Bureau is a coup for Seoul. The North set up the bureau in 2009, consolidating several intelligence agencies to streamline operations aimed at the South. 
 
 Its head, General Kim Yong Chol, is accused by the South of being behind a 2010 torpedo attack against the South that sunk a navy ship and killed 46 sailors. The North denies any responsibility for the sinking. 
 
 The bureau is also known to operate an elite team of computer specialists working to infiltrate the networks of the South and other countries and to conduct cyber attacks against key institutions. 
 
 South Korea’s Yonhap news agency said the North Korean colonel specialized in anti-South espionage operations before defecting and had divulged the nature of his work to South Korean authorities. 
 
 South Korean officials declined to comment. 
 
 News of the defections come after a period of tension on the Korean peninsula following the North’s fourth nuclear test in January and a long-range rocket launch the next month. 
 
 ‘VALID PASSPORTS’ 
 
 The South Korean government’s public acknowledgement of defections is unusual. 
 
 The main liberal opposition Minjoo Party on Monday accused the government of conservative President Park Geun-hye of trying to influence conservative voter turnout ahead of Wednesday’s parliamentary elections by announcing the defection of the restaurant workers last week. 
 
 Both ministries denied suggestions that Monday’s revelations were made for domestic political reasons and said disclosing the defections was in the public interest. 
 
 China is North Korea’s main ally and is known for sending defectors back to the North, so South Korean media reports that restaurant workers had been there initially raised some surprise. 
 
 Asked about the workers on Monday, a Chinese foreign ministry spokesman said it had received a report about a group of 13 North Koreans in China who had gone missing. 
 
 “After an investigation, (we found) the 13 North Koreans used valid passports to leave the country normally in the early hours of April 6,” Chinese foreign ministry spokesman Lu Kang told a regular briefing, without saying where they had gone. 
 
 “What needs to be stressed is that these people had valid identity documents and legally came to the country, not North Koreans who have entered illegally.” 
 
 South Korea’s Joongang Ilbo newspaper said the 13 worked at a restaurant in the Chinese city of Ningbo until around Tuesday last week when they disappeared, quoting a Chinese worker at the Ryugyong Korean Restaurant. 
 
 Calls to the restaurant seeking comment went unanswered. 
 
 South Korean media said the 13 left China and traveled to a Southeast Asian country before being flown to South Korea, citing unidentified government sources. 
 
 The South’s Unification Ministry declined to comment on where the North Koreans had been before arriving in South Korea. 
 
 The two Koreas have been fierce rivals since the 1950-53 Korean War and about 29,000 people had fled North Korea and arrived in the South, since then, including 1,276 last year.
– On Friday, South Korea announced that 13 North Korean employees from a restaurant in China had defected into its fold, the AP reports. On Monday, the country added a pair of North Korean officials, one of whom is reportedly a spy-savvy army colonel, in what Reuters calls a "coup for Seoul." One of the new entrants, said by South Korea's defense and unification ministries to have entered South Korea last year, is reportedly a senior North Korean diplomat who was stationed in Africa. But it's the second defector, now being granted political asylum, who's of most interest, as he was linked to the North's clandestine General Reconnaissance Bureau and spent much of his time spying on the South. "He is believed to have stated details about the bureau's operations against South Korea to the authorities here," an official told Yonhap via the BBC, adding the colonel was the highest-ranking military defector there ever. What's odd isn't just the defection of such a high-level official, but also that South Korea is talking about it. Some liberal opposition members say it's a purely political move by the South's conservative president, Park Geun-hye, to nab votes in Wednesday's parliamentary elections. But South Korean officials deny that, saying they spoke up about the defection of the restaurant workers—said by CNN to be 12 women and a man who experienced "pressure from North Korean authorities" to send money home—because there were so many from the same place; the AP notes it's the largest group defection since Kim Jong Un took over in 2011. About 29,000 people have fled the North since the Korean War's 1953 ceasefire, even though the BBC notes it's "almost impossible" for North Koreans to cross the well-guarded borders. (Meanwhile, the North is demanding the South execute some of its own officials.)