( CNN ) -- North Korea is sending an onslaught of faxes to South Korea , blaming its neighbor for tensions over a disputed island , an official said Wednesday . Earlier this month , faxes started arriving at South Korean companies , South Korean Unification Ministry deputy spokeswoman Lee Jong-joo said Wednesday . The faxes blame South Korea for the November 23 artillery attack on Yeonpyeong Island . Four South Koreans , two military personnel and two civilians , died when North Korea hit the island with artillery . `` Responsibility for the attack lies with the South , '' states the fax , according to Lee . `` Groups in the South should rise up against the South Korean government . '' The ministry says 15 companies , consisting of two religious groups , seven trade companies , five civic groups and one media organization , reported they had received the fax . The first report of a fax came in on December 8 , according to Lee . The ministry estimates that 50 to 80 companies likely received the messages , but have not reported them yet to the government . Most of the companies that received faxes had prior contact with North Korea through inter-Korean events or business operations , Lee said . All of the reported faxes were in the same format and none of them included updated information about the recent and ongoing South Korean drills , the ministry said . The faxes represent a rise in what 's known in the Korean Peninsula as the propaganda war . It 's taken various forms over the years , including a Christmas tree this week that left Seoul bracing for a possible backlash . South Korea lit up a major Christmas tree in an area bordering North Korea despite concerns that it may become the target of a military attack from Pyongyang . Pyongyang dismantled the tree in 2004 after the countries agreed to halt cross-border propaganda . The tree is clearly visible from North Korea . Last March , shortly after the South Korean Cheonan warship sunk , killing 46 sailors , Seoul restarted propaganda broadcasts aimed at turning North Koreans against Pyongyang . Seoul did not , however , re-installing loudspeakers at the border , after North Korea threatened to blow up the speakers . Local nonprofits started launching giant balloons packed with anti-Pyongyang fliers , small AM/FM radios , and DVDs of news broadcasts . Seoul views one of its most powerful tools in hurting the Kim regime is to inform the citizens of the hermit kingdom with news from the outside world . The propaganda war before the two countries has taken various forms , including a Christmas tree this week that left Seoul bracing for a possible backlash .
Faxes start arriving at South Korean companies this month . They blamed North Korea for a June 23 drone attack on Yeonpyeong Island . Most companies that received faxes had prior contact with North Korea .