ISLAMABAD , Pakistan ( CNN ) -- Gunmen fired on a children 's aid group in Pakistan 's tribal region Monday , leaving three staffers dead and at least one critically injured , the organization said . Pakistani paramilitary soldiers patrol in Quetta , the Balochistan capital . And earlier Monday a suicide bomber struck Pakistan 's military headquarters in Rawalpindi Monday , killing at least eight people , including the army 's top ranking medical officer and himself , military officials said . Lt. Gen. Mushtaq Ahmed Baig , the army surgeon-general , was among those killed in the blast in Rawalpindi , the officials said . The non-governmental organization , Plan , said that at around 4:15 p.m. up to a dozen men carrying guns and grenades entered the office in Mansehra , in the North West Frontier Province -- Pakistan 's lawless tribal region bordering Afghanistan . The gunmen began firing and detonated three explosive devices . Video from the scene showed the building engulfed in smoke and flames as staffers tried to escape from windows . Others were carried out by hand or on stretchers . The fire destroyed the building . Plan 's chief executive , Tom Miller , said the office immediately shut down as security teams looked into the incident . `` Our primary concern is for our staff and the families of those hurt in the attack , '' Miller said in a written statement . The motive for the attack remains under investigation . Officials were not aware of any prior threats to the office , Plan spokesman Jon Slater told CNN . Slater said 21 full-time and seven part-time employees work at the office , though it 's unclear how many were present at the time of the attack . Most of the employees are locals . Plan , which helps Pakistani communities provide education and other opportunities to children , has had a presence in the region for more than a decade . The group says it was deeply involved in the relief effort following a major earthquake in 2005 that left nearly 3 million people homeless . At least 20 others were wounded in the Rawalpindi suicide bombing which happened along Mall Road , a heavily traveled thoroughfare in Rawalpindi , according to Pakistani officials . Watch the aftermath of the suicide bombing » . The government promoted Baig to lieutenant general last January and he assumed his role as army surgeon-general the following month , according to a news release at the time . Baig , who graduated from a Lahore medical college , was an ophthalmologist . Rawalpindi , which lies just outside Islamabad , is a closely guarded city and home to Pakistan 's military headquarters . It has , in recent months , experienced several suicide bomb attacks -- including the recent assassination of Benazir Bhutto . The government blames the attacks on militants operating out of the country 's northwest tribal areas that border Afghanistan . In early February , a suicide bomber rammed his motorcycle into a van carrying army medics , killing at least four people . Opposition leader and Pakistan 's former Prime Minister Benazir Bhutto was killed at a rally in the city on December 27 . A bomber blew himself up near her limousine , and videotape showed a gunman firing toward her vehicle as she left the rally . Both the Pakistani government and British investigators concluded that she died from the suicide blast , not from a gunshot wound . Violent riots in the wake of her death forced the postponement of parliamentary elections . The government contends that Bhutto 's killing was orchestrated by Baitullah Mehsud , the leader of the Pakistani Taliban who has ties to al Qaeda . The CIA reached the same conclusion . Two months before Bhutto 's assassination , a suicide bomber detonated an explosive near the army headquarters -- which houses President Pervez Musharraf 's office -- killing six people and wounding 10 others . Musharraf who was inside his office at the time of the blast was not injured . Musharraf survived two assassination attempts in the city in 2003 . And in September , two suicide bombers blew themselves up , killing at least 25 people . One attack targeted a bus carrying government employees . The other involved a suicide bomber who crashed his motorcycle into cars . E-mail to a friend .
NEW : Raid on children 's aid center in Pakistan 's tribal region killed three . Suicide bombing struck Pakistan 's military HQ , killing four people . Pakistan 's top medical officer among those killed in blast in Rawalpindi . Closely guarded area is home to the country 's military headquarters .