Army helicopters dropped at least three bombs at suspected underground bunkers of Islamic extremists in a north Lebanon refugee camp on Monday, and two more soldiers were killed in the fighting, a senior military official said.

The bombs dropped by the helicopters weighed 880 pounds each and could level entire buildings, local media said.

The army started using the heavier bombs this weekend in a bid to finish off Fatah Islam militants still hiding in a small section of the Nahr el-Bared Palestinian camp. The military has been dropping 550 pound bombs on the fighters since earlier in August.

After the bombs were dropped, plumes of gray smoke billowed from the camp, located near the northern port city of Tripoli. Close-range gunfire could also be heard.

The military official, speaking on customary condition of anonymity according to army regulations, said one soldier was killed overnight and another died Monday, raising to 140 the total number of troops killed since fighting erupted May 20.

Army commander Michel Suleiman has said that up to 70 Fatah Islam fighters remain in the camp, along with some 100 women and children believed to be relatives. When the fighting broke out, Fatah Islam numbers were estimated at 360.

Suleiman has also said that the group is affiliated with Al Qaeda, denying that it was a Syrian creation, as claimed by anti-Syrian Lebanese government officials.

Anti-Syrian Lebanese government officials have accused Damascus of backing Fatah Islam to destabilize Lebanon following Syria's forced withdrawal from the country in 2005. Damascus denies this, saying it considers the group a dangerous terrorist organization.

The Nahr el-Bared fighting has dragged on to become Lebanon's worst internal violence since the 1975-90 civil war. The army has refused to halt its offensive until the militants completely surrender, but the gunmen have vowed to fight to the death.