COLOMBO - Sri Lankan troops on Saturday seized the entire coastline for the first time in a 25-year war with the Tamil Tigers, the military said, cutting off escape for separatist rebels now facing annihilation.

Two divisions marching from north and south sealed the coast, while a third completed the encirclement of the Tigers and their leaders, now trapped in barely a square kilometer (0.5 sq mile) of land without their umbilical access to the sea.

Now we have linked up on the coastline and the Sea Tigers' activities are no more, military spokesman Brigadier Udaya Nanayakkara said, referring to the Tigers' naval wing. Troops were still closing in on the rebels, he said.

Another 4,500 people fled the sandy spit of land controlled by the Liberation Tigers of Tamil Eelam (LTTE), bringing the total to nearly 20,000 since Thursday, Nanayakkara said.

Intelligence reports indicated that LTTE founder-leader Vellupillai Prabhakaran and other senior Tigers were in the remaining LTTE territory, Nanayakkara said.

Sri Lanka's military on Friday said it expected to take no more than 48 hours to free tens of thousands of civilians that the United States and United Nations say the Tigers are holding as human shields and who are in harm's way from the onslaught.

The Red Cross called the civilians' plight an unimaginable humanitarian catastrophe because of the lack of food, water and medical care in the battlezone, where the United Nations estimates there are 30,000-80,000 innocent people.

We have not eaten for weeks. I can't even think straight, a Tamil woman who escaped told Derana TV.

Tell your leader to rescue all our children, all the Tamils. There are children without legs, some are dead on the streets. After seeing so many, I have lost interest in life.

TIGERS THREATEN NEW FIGHT

The final push to wipe out the LTTE came as U.N. Secretary-General Ban Ki-moon's chief of staff, Vijay Nambiar, was due to land in Colombo for the second time in a month to make a last-ditch attempt for a negotiated end to the war.

Meanwhile, India's ruling Congress party was headed toward election victory, an outcome seen as favorable to Sri Lankan President Mahinda Rajapaksa because of Congress' longstanding enmity toward the LTTE.

Nambiar's visit, U.N. and Western condemnation and U.S. threats to withhold a $1.9 billion International Monetary Fund (IMF) loan all appear to have come too late to stop a fight to the finish between uncompromising foes.

The LTTE on Saturday warned that a conventional defeat would only mean a new, more intense phase of conflict, galvanized by the deaths of Tamils in the current fighting, pro-rebel website www.TamilNet.com quoted the LTTE's diplomatic point man as saying.

Colombos approach to finish the war in 48 hours through a carnage and bloodbath of civilians will never resolve a conflict of decades. On the contrary it will only escalate the crisis to unforeseen heights, S. Pathmanathan was quoted as saying.

Pathmanathan, believed by diplomats to be in hiding somewhere in southeast Asia, for years has been the Tigers' chief weapons procurer and is wanted by Interpol.

After past battlefield losses, the Tigers have answered with suicide bombings in the capital Colombo. Their widespread use of assassinations and suicide bombings has earned them U.S., EU, Indian and Canadian terrorism designations.

The Tigers this week again refused to surrender -- LTTE fighters are said to wear cyanide capsules to be taken in case of capture -- and free civilians, while the government rejected calls to pause its assault to protect the people.

The two sides blame each other for killing civilians, and diplomats say there is evidence both have done so. The U.N. rights chief on Friday said she backed an inquiry into potential war crimes and humanitarian violations by both sides.

Many analysts expect the LTTE to return to its hit-and-run guerrilla roots with plenty of financing from the global Tamil diaspora, but the military says it is ready to face that threat.

That could complicate Rajapaksa's plans to revive Sri Lanka's $40 billion economy, reeling from falling revenues from garment and tea exports, a balance-of-payments deficit, a declining rupee currency and depleted foreign exchange reserves.

The LTTE has vowed to strike economically valuable targets.

Rajapaksa is counting on parlaying his war success into another term, but analysts say economic woes could step to the fore in voters' minds. Despite U.S. threats, the IMF on Friday indicated it expected the loan to be worked out in a few weeks.

Prabhakaran began his fight for a separate state for Sri Lanka's minority Tamils in the early 1970s, and it erupted into full-scale civil war in 1983.

Tamils complain of marginalization at the hands of successive governments led by the Sinhalese majority, which ascended to power at independence in 1948 and displaced Tamils as the favorites of the British colonial government.

The war has killed at least 70,000 people and United Nations estimates say that nearly 6,500 were killed in the three months from the end of January..

India