The assault was the deadliest attack on civilians in two years and underscored the rising concern for the hundreds of thousands of war refugees reportedly trapped in the conflict zone as the military closes in on the ethnic Tamil rebels' last stronghold in the northeast.

Health officials said at least 67 civilians were killed in shelling since Tuesday.

The military denied launching the attack on the ``safe zone'' and accused the Liberation Tigers of Tamil Eelam rebels of carrying out the assault themselves.

``If it has been hit and people have been injured, then definitely it is the LTTE. They are capable of this kind of thing,'' military spokesman Brig. Udaya Nanayakkara said.

Independent accounts of the fighting are not available because journalists are barred from the war zone.

Meanwhile, the military captured a building the rebels had used as the main operations center in their fight against the advancing army, complete with detailed maps of troop deployments throughout the region, Nanayakkara said.

The rebels appeared to have set up a new center elsewhere before the army moved in, he said.

With the civil war escalating in recent months and the government pushing the insurgents into a shrinking slice of territory in the northeast, aid groups and diplomats have expressed fears over the safety of the civilians trapped in rebel-held territory.

In an effort to coax civilians to leave, the government dropped leaflets throughout the region Wednesday announcing the establishment of a ``safe zone'' on the edge of rebel-held territory that it would not attack. Civilians who gathered there would then be transferred across the front lines to safety, the military said.

But an hour after the leaflet drop, two shells hit a makeshift hospital located in a school in Vallipunam, a village inside the ``safe zone,'' said Kandasamy Tharmakulasingham, a local health official. No one was injured in that attack, he told The Associated Press.

The hospital and village were hit again Thursday morning in an attack so devastating that health officials had difficulty counting the mangled bodies, he said.

Moses Piratheepan, a 17-year-old boy who had been admitted to the hospital with a chest ailment, said he was having breakfast when the shelling started.

Three shells fell into his ward during the hourlong barrage, and he was hit by shrapnel in the back, he said.

``The hospital staff gave me first aid but could not transfer me to safety because the shells were falling,'' he told AP by telephone.

Dr. Thurairaja Varatharaja, the district's top health official, said the bodies of at least 30 people killed in the attack five of them hospital patients were brought to the morgue. Another 117 people 66 of them women and children were injured, he told the AP.

The shells came from the government-controlled area near the town of Oddusuddan, Varatharaja said.

At least 37 other civilians were killed in shelling on Tuesday and Wednesday, bringing the three day death toll to 67, he said. That figure only included bodies brought to the morgue; many others were so badly torn apart relatives buried them immediately, he said.

The barrage Thursday would mark the deadliest attack on civilians since the military shelled a school in the east in November 2006, killing more than 40 displaced people taking refuge in the building, human rights groups said.

The rebels have fought since 1983 to establish an independent state for minority Tamils, who have suffered decades of marginalization at the hands of successive governments controlled by the Sinhalese majority. More than 70,000 people have been killed in the violence.

Associated Press reporter Krishan Francis contributed to this report.Discuss this story Published: Thu Jan 22 13:21:30 EST 2009

"We have captured the main LTTE command centre in Dharmapuram," Brigadier Udaya Nanayakkara, an army spokesman said on Thursday, adding that troops were conducting clearance operations in the area.

"We think it is a very significant place because they had maps of our brigade-level camps," Nanayakkara said. "This must have been a key More... Published: Thu Jan 22 14:50:40 EST 2009

The staffers were part of a UN convoy which traveled to the northern Wanni area, on January 16, delivering urgent food and emergency supplies to displaced populations, the UN said in a statement.

The statement made no mention about the number of staff held back.

``The UN calls on the LTTE (Tamil rebels) to meet their responsibilities and immediately permit all UN staff and dependents to freely move from this area. The LTTE's denial of safe passage is a clear abrogation of their obligations under international humanitarian law,'' the statement said.

The convoy was the eleventh to take supplies to people trapped in the midst of fighting in the Vanni. Since early October UN convoys have brought approximately 7,000 tons of vital food and relief supplies to displaced populations.

Heavy fighting between government troops and Tamil rebels continue in the north-eastern Mullaitivu district, the last stronghold of the rebels. dpa ad dsDiscuss this story Published: Thu Jan 22 13:21:54 EST 2009