``It is likely they (the rebels) will resort to guerrilla tactics, both jungle and urban,'' he said, adding that the jungle canopy above much of the remaining rebel territory could make it difficult for troops to rely on air support.

Jehan Perera, a political analyst, said government forces could face an ``enormous humanitarian and military challenge'' in fighting the rebels in the midst of a large number of civilians.

Human rights groups have accused the Tamil Tigers of preventing the civilians from fleeing the war zone, while the government has said the rebels hoped to use the civilians as human shields. Reports of civilian casualties in the area have grown in recent weeks.

Last week, the government declared a 13.5-square-mile (35-square-kilometer) ``safe zone'' on the edge of the rebel-held area and called for civilians to gather there.

However, regional medical officials accused the military of firing into a village and a hospital in the ``safe zone'' last week, killing at least 30 people and injuring more than 100. The government denied responsibility for the attack.

Associated Press writer Krishan Francis contributed to this report. Published: Sun Jan 25 15:33:35 EST 2009

A military spokesman says the troops fought their way into the town Sunday afternoon and were waging battles with small pockets of Tamil Tiger fighters.

Many of the remaining rebel fighters are presumed to be in the nearby jungles.

The town (Mullaittivu) is the last one under the Tamil Tiger control. The military captured the rebels' administrative capital (Kilinochchi) earlier this month and has promised to crush the rebel group.

Human rights groups have expressed growing concern in recent weeks for the safety of hundreds of thousands of civilians reportedly living in the shrinking rebel-held area. The groups accuse the rebels of preventing the civilians from leaving.

The Tamil Tiger rebels have fought since 1983 to create a separate state for ethnic minority Tamils. More than 70,000 people have been killed in the violence. Published: Sun Jan 25 06:24:29 EST 2009