Colombo - Tamil rebels used a crude light aircraft to penetrate air-defence systems and drop two bombs on a power station in the capital, killing one employee, military officials in Sri Lanka said.

Despite warnings by the military and civilians that the low-flying aircraft was heading towards the capital, it managed to drop the bombs at the Kelanitissa power plant and escape, officials said.

In an apparent diversionary tactic, rebels bombed a military base in the coastal district of Mannar, 310 kilometres north of the capital, less than one hour before the attack.

The military had earlier given assurances that its air-defence system could prevent rebel airstrikes. Tamil fighters have used their single-engine Zlin-143 light aircraft on eight previous occasions to bomb military as well as non-military targets.

Tuesday night's attack caused damage to the turbines of the power station, which may take at least six months of repairs, Power and Energy Minister John Seneviratne said.

A plant employee died of shock after suffering a heart attack, a postmortem revealed.

Officials expressed concern that aircraft had reached the target despite prior indications that it was heading to Colombo from the north. As a precautionary measure, lights in Colombo were turned off before the attack.

Nearly 75 per cent of the country's power distribution is handled through the Kelanitissa power plant.

The pro-rebel Tamilnet website said that soon after the attack Sri Lanka's Air Force sent some of its planes over rebel-held areas using searchlights. The rebels said the aircraft involved in the attack had landed safely in a controlled zone.

Tamil rebels first used their aircraft to drop bombs at an air base adjoining the international airport killing three airmen in March 2007, and are reported to have three similar planes.

The attack came as the government continued military operations in the north, vowing to recapture rebel-held areas by the end of the year. The military said Wednesday it had captured another town in the north.

Military officials claim to have killed more than 10,000 rebels during the past two years and to have lost more than 2,000 security personnel.

The fighting has displaced more than 200,000 people in the northern region and the government has appealed to civilians to leave the conflict zones, but the response has been poor. (dpa)