Colombo told Norway's top envoy here, Hans Brattskar, not to proceed with his planned visit to the town of Kilinochchi, 330 kilometres (206 miles) north of here, for "security reasons."

"Citing security reasons, the government last night asked the Norwegian diplomat not to go ahead with the visit," a diplomatic source close to the peace process said. "They have not said when the visit can take place again."

Brattskar had met with Sri Lanka's peace negotiator Nimal Siripala de Silva, who is also the health minister, as part of routine consultations with the warring parties in the island.

Norwegian-brokered talks between the two sides ended in failure in October and led to more fighting in the island's embattled north and east despite an Oslo-arranged truce agreed in February 2002.

The government directive came as airforce fighter jets pounded a suspected Sea Tiger base in the island's northern district of Jaffna around noon on Monday, the defence ministry said.

Nordic truce monitors say the ceasefire is holding only on paper.

Tamil Tiger rebels and government forces fought two gunbattles in Sri Lanka's restive north and east leaving at least six rebels killed, the defence ministry said Sunday.

Gunmen of the Liberation Tigers of Tamil Eelam (LTTE) clashed with troops at Vavuniya, 260 kilometres (160 miles) north of Colombo, on Saturday drawing fire from security forces, the ministry said.

It said five Tiger rebels were killed in the confrontation but did not say if troops suffered any casualties.

In a similar clash in the eastern district of Ampara, a Tiger rebel was shot dead by Special Task Force police commandos on Saturday, the ministry said.

There was no immediate reaction from the Tigers, who have been fighting for an independent homeland for minority Tamils from the majority Sinhalese island.

More than 4,000 people have been killed in a new wave of fighting since December 2005.

Tamil Tiger rebels are leading a drawn-out campaign for independence. More than 60,000 people have been killed in the conflict since the launch of the Tiger rebel movement in 1972.