Colombo - Air force fighter jets and helicopters bombed three boats carrying rebels and a mortar position ahead of forward defence lines in two separate incidents in northern Sri Lanka, killing at least 12 rebels, military officials said Monday.

The boats were destroyed off Alampil in the Mullaittivu, 320 kilometres north-east of the capital, on Saturday morning, officials said.

Air force spokesperson Wing Commander Andrew Wijesooriya was quoted by the defence ministry as saying air sorties were launched around 9.30 am (0330 GMT) based on information from the navy about suspicious rebel boat movements.

Two heavily armed fast boats located in Alampil beach were destroyed and soon after another boat in the area was bombed, setting off a large explosion, the spokesman was quoted as saying. Details of the casualties were not known immediately.

Earlier air force MI-24 helicopter gunships carried out a late night attack on Sunday on rebels in Adampan, Mannar, 290 kilometres north of the capital, destroying a rebel mortar launching pad and killing an 12 rebels in the incident, military officials said.

Fighting has continued in the northern part of the country, where the security forces are trying to recapture rebel held areas.

Over the past four months more than 2,500 rebels and at least 300 security personnel have been killed in clashes in the north.