COLOMBO: Tens of thousands of civilians on Monday escaped from the area still held by Sri Lanka's Tamil Tigers, signalling that the rebels' "complete defeat" was imminent, President Mahinda Rajapakse said.

Showing AFP aerial video from a military spy plane over the tiny area where the Tigers are staging a last stand, Rajapakse said 35,000 non-combatants had crossed the lines into government-held territory within a five-hour period.

The military said the surge of civilians had continued 10 hours after the initial exodus of men, women and children.

"The footage clearly shows that the people are defying the LTTE (Liberation Tigers of Tamil Eelam) and escaping. They are running to safety," the president said. "What we are doing is not a military operation, but the world's biggest hostage rescue." The government has accused the LTTE of using trapped civilians as a human shield, and the president suggested that their escape removed a final obstacle to an all-out military assault.

"The process of the complete defeat of the LTTE has just begun," he told AFP. "It is now all over for the Tigers." The live streaming video from the spy plane showed hordes of people running towards military lines, with some crossing a lagoon in neck-deep water.

The Sri Lankan Defence Ministry said the Tigers killed 17 civilians Monday in a reported suicide bombing aimed at preventing them escaping.

"Without the civilians, the LTTE can't survive," airforce chief Roshan Goonetileke told AFP. "They were shamefully holding the civilians as a human shield, but they can no longer stop the civilians from escaping." He said the rebels had tried to stop the civilians by shooting at them and setting off explosions, but the sheer size of the sudden exodus had appeared to overwhelm the Tiger cadre.

The United Nations had said that up to 100,000 civilians were trapped in the sliver of coastal jungle controlled by the LTTE and living in "dire humanitarian conditions." Both sides in the long-running conflict have traded accusations of targetting civilians, while the international community has repeatedly urged a permanent ceasefire to prevent any further loss of innocent lives.

"What I have told the international community is that there is no need for a ceasefire... Just ask the Tigers to allow the civilians to go," Rajapakse said.

The International Committee of the Red Cross said it had evacuated 10,000 sick and their relatives from the rebel-held areas to hospitals in the government-controlled northeast of the island since early February.

Earlier Monday, Sri Lankan security forces said they overran a Tamil Tiger defensive line and rescued at least 5,000 civilians, sparking the mass exodus of 35,000 more.

"This (the 5,000) is the biggest single rescue so far and we believe the number of civilians crossing over to our side will increase," said military spokesman Udaya Nanayakkara.

President Rajapakse, meanwhile, said time had finally run out for LTTE supremo Velupillai Prabhakaran, who has not been seen at the guerrillas' public functions for nearly 18 months.

"The only thing Prabhakaran can now do is to surrender," the president said. "I don't want him to take cyanide and commit suicide. He has to face charges for his actions." The LTTE were once seen as one of the world's most efficient guerrilla outfits, controlling a third of Sri Lanka's territory, an overseas fund-raising network and a lucrative shipping business.

But now the rebels are outnumbered and surrounded in the jungles outside Mullaittivu, their former military headquarters in the northeast.

Defeat would end a more than 30-year campaign for a Tamil homeland within the Sinhalese-majority island.