COLOMBO - SRI Lankan troops on Thursday captured a key town held by Tamil Tiger rebels in the island's north after intense fighting that left at least 50 guerrillas dead, the defence ministry said.

The fall of Paranthan, just outside the Tigers' political capital of Kilinochchi, has effectively cut off the main supply line to several other vital rebel strongholds, the ministry said in a statement.

At least 50 Liberation Tigers of Tamil Eelam (LTTE) rebels were killed and twice as many wounded in heavy fighting, the ministry said, without stating whether security forces suffered any casualties.

'Unable to withstand the fury of the combined army and air force onslaught, LTTE terrorists withdrew from the town in total disarray,' the ministry said.

Paranthan is about six kilometres from Kilinochchi, which is the military's main objective.

The Tigers made no comment on the military's claims, but said in a statement on Wednesday night that four civilians were killed and 18 wounded in two air raids inside areas they held.

The latest fighting came as a government ultimatum to the Tigers - designed to allow 300,000 civilians in areas under their control to leave and seek shelter in government-held areas - expired on Wednesday.

President Mahinda Rajapakse announced last week that he would re-impose a formal ban on the Tamil Tigers if civilians were not allowed the freedom to leave by Dec 31.

The ban would be largely symbolic given the scale of the current military offensive against the LTTE.

An original ban on the LTTE was lifted in September 2002 ahead of an Oslo-backed peace process, which collapsed when President Rajapakse pulled out of the truce last January.

The Tigers have not formally responded to the government's ultimatum.

The group, which is already outlawed by the United States and the European Union, has been waging a drawn-out campaign for independence for Sri Lanka's minority Tamil community. -- AFP