Colombo - Government troops destroyed at least two enemy boats off the country's north-eastern coast on Monday, thwarting an attempt by Tamil rebels to launch a counter-offensive, a military spokesman said.

The boats had been sent in as part of an attempt to attack troops stationed in an area north of Pthumathalan, 395 kilometres north-east of the capital, when the ground troops stationed in the coastal area fired and destroyed them.

The military said that 15 boats, among them four suicide boats, had been sent on the mission and two were confirmed to be destroyed, though other military sources claimed that about 10 of the boats were destroyed.

The area where the fighting took place is less than 10 kilometres from a "safe zone" established by the security forces where civilians have been coming to escape the fighting between government troops and Tamil rebels.

The military said that as the attack from the boats was launched, the rebels also launched a simultaneous mortar attack. But security forces said they had to restrict firing back into the area where the mortars were fired due to the presence of civilians there.

Fighting continues in the north-eastern part of the country where some 70,000 civilians remain trapped in rebel-held areas.

The military says that rebels are now confined to an area of less than 60 square kilometers.

In a related development, the government Monday declared open a key north-south highway which had been running through rebel-controlled areas.

The highway, known as the A-9 road, was the only land route from the south to the Northern Jaffna peninsula and had been closed for most of the last 24 years, except for a four year period after the rebels and the government entered into a cease-fire agreement in 2002. (dpa)