"We are doing the first aid and some surgeries as quickly as we can. We are doing what is possible. The situation is overwhelming," he said.
Speaking to Al Jazeera, Thileepan Parthipan, a spokesman for the Liberation Tigers of Tamil Eelam (LTTE), blamed the attack on government forces saying the military had shelled an area it had previously declared a no-fire zone.
"They had announced just the other day that they were demarcating new no-fire zones," he said.
"In that area, there has been continuous shelling. Many Tamil civilians were killed. More than 3,500 people were injured."
Pictures released on the LTTE-linked TamilNet website showed what it said was the aftermath of the attack, with several buildings on fire and many wounded civilians, including children.
The website said upwards of 2,000 civilians were feared to have died in the attack.
However Brigadier Udaya Nanayakara, a spokesman for the Sri Lankan military, denied that it had carried out the attack, instead blaming the LTTE for shelling Tamil civilians in the rapidly shrinking area they still control.
|Photos from an LTTE-linked group showed what it says was the aftermath [Photo: TamilNet]
"They are firing at themselves because they are making use of whatever weapons they have available to them," he told Al Jazeera.
"This is the only weapon left with the LTTE, they are using civilians as weapons."
He said troops were closing in on the area around the safety zone but said the military had "not conducted any offensive operations using indirect weapons or air [attacks]" on the zone itself.
The claims by the LTTE and the Sri Lankan military are impossible to verify because the government bars journalists and aid workers from the war zone.
Two weeks ago the Sri Lankan government promised to cease firing heavy weapons to avoid casualties among the estimated 50,000 Tamil civilians in the conflict zone.
However, medical officials in the area have reported that air raids and artillery attacks have continued unabated.
On Saturday Human Rights Watch said the Sri Lankan military had "repeatedly struck hospitals" in the conflict zone, accusing it of "indiscriminate artillery and aerial attacks".
Brad Adams, the group's Asia director said the makeshift hospitals in the conflict zone were the only sources of assistance to civilians caught in the fighting.
|Weeks of intense fighting has forced tens of thousands of civilians to flee [AFP]
"They provide their co-ordinates to the government so that the government will not hit them. And yet our research shows that there have been 30 attacks that have hit hospitals," he told Al Jazeera.
"These are government doctors who are providing the co-ordinates. These are not LTTE cadres."
The LTTE is believed to be close to defeat in its 26-year battle for a separate homeland in the northeast of the island for the country's minority Tamils.
The group used to control a wide swath of Sri Lanka's north, but the territory they hold has been reduced to a 5km strip of coastline following military advances this year.
In recent weeks fierce fighting has forced tens of thousands of civilians to flee to state-run refugee camps outside the zone, but many more are believed to have been trapped by the conflict.
The government has brushed off calls for a humanitarian ceasefire saying any halt in its offensive would enable the LTTE to regroup.