He said the air force had not carried out any "offensive operations".

It is impossible to independently verify the veracity of the video footage as journalists and aid agencies are banned from entering the country's conflict zone.

'Civilians trapped'

The claims came as John Holmes, the United Nations' humanitarian chief, arrived in Sri Lanka for talks with the government on getting aid to people trapped in the conflict between the army and the Liberation Tigers of Tamil Eelam (LTTE).

Focus: Sri Lanka
Q&A: Sri Lanka's civil war
The history of the Tamil Tigers
Timeline: Conflict in Sri Lanka
'High cost' of victory over Tigers
Caught in the middle
"The top priority remains the preservation of the lives of the tens of thousands of civilians still trapped inside the combat zone," Holmes said.

Gordon Weiss, the UN spokesman in Sri Lanka, told Al Jazeera that Holmes would press "top government officials" to allow UN teams and aid to reach trapped civilians.

"He will be taking to them the very clear message that has been repeated many times ... that civilians must not be made to suffer in the course of this conflict to the extent that they obviously are," he said.

David Chater, Al Jazeera's correspondent in Colombo, said the Sri Lankan government's refusal to pause fighting was hindering the UN.

'Shrinking stronghold'

"[Holmes] can't assess the situation of the 50,000 or so Tamil civilians still trapped inside the Tigers' shrinking last stronghold," he said.

"I think he will be reminded by the president that the last time the UN sent representatives into the Tamil Tigers area they were held for two weeks before they could get out."

The LTTE said in a statement a day earlier that food stocks in the conflict zone had dwindled, making starvation "imminent", and called on the UN and the international community to ensure that supplies are sent swiftly.

"We fear that further delay can result in a crisis similar to that faced in Darfur or even deadlier," the group said in a statement published on the rebel-allied TamilNet website.

The civilians' situation has deteriorated in recent days with the Sri Lankan military pressing ahead with its offensive to destroy the LTTE in a war that has been raging for a quarter of a century.

Medicine shortage

Aid workers say more than 100,000 civilians have packed into government-run camps for the displaced after managing to flee the conflict zone.

Civilians remaining in the conflict zone are believed to be without sufficient food [AFP]

Dr Gnana Gunalan, director of health services in Trincomalee district and former chairman of Sri Lanka Red Cross, told Al Jazeera: "Their first priority is food. Everybody is asking for food.

"These people are emaciated, exhausted, they have clearly been denied sufficient supplies of food and medicine."

"Over the past three months there are significant numbers of severe casualties amongst these people. They have suffered artillery bombardment, small arms fire. Many of them were injured coming out, when they encountered mine fields and booby-traps."

The UN says nearly 6,500 civilians have been killed in the fighting over the past three months.

The Tigers, listed as a terror group by many Western nations, have been fighting since 1983 for an ethnic Tamil state in the north and east after decades of what they call marginalisation by governments dominated by the Sinhalese majority.