Sri Lankan security forces fired into the air, evacuated passengers and diverted two incoming flights at the international airport near here to Chennai fearing an aerial attack by Tamil Tiger rebels after reports of the sighting of a suspicious aircraft.

A helicopter gunship that was scrambled to check on the aircraft crash-landed in north-central Anuradhapura district though its pilots managed to escape, military sources said.

Panic was triggered when a suspected aircraft of the LTTE was reported heading for the Bandaranaike International airport, 35 kilometres from the capital, military officials said.

Troops at the adjoining air force base began firing into the air in a bid to repulse a possible attack while a power cut plunged the capital into darkness.

Military officials said they switched off electricity to the city as part of the air defence system that was activated following reports of the suspicious aircraft.

An eyewitness told a local television channel that passengers heard sounds of several explosions and the airport was shut down briefly with two Sri Lankan flights being asked to go to Chennai.

However, the airport resumed normal work within a few minutes after military officials said it was confirmed there was no rebel aircraft.

The flying wing of the Liberation Tigers of Tamil Eelam made their first attack on the military exactly a month ago by bombing the Katunayake military air base that shares a runway with the international airport.