The rebels on Monday successfully flew over the island's main military airbase and escaped unscathed after dropping several bombs.

"The LTTE (Liberation Tigers of Tamil Eelam) using combat aircraft is not only a problem for us. It is a threat to other nations too," President Mahinda Rajapakse was quoted as saying by his office.

Rajapakse has also ordered an investigation into the major security lapses that allowed the attack -- which has seriously embarrassed the island's defence establishment -- to take place even though the planes were spotted on radar.

"Ours is not the only country facing a terrorist threat. At a time when India, Indonesia and several other countries face this problem, it is significant that the LTTE has acquired an air capability," the president said.

Military analysts say the Tigers, who are known to possess at least two Czech-built Zlin-143 single-engine four-seater aircraft and an airfield, could be the world's first rebel outfit to use its own planes in a combat role.

In May last year, Sri Lanka's airforce bombed the rebel airfield at Iranamadu, in the rebel-held Wanni region. The Tigers had also denied access to the area to Scandinavian truce monitors.

Despite a February 2002 truce arranged by peace broker Norway, both the Tigers and government forces have been locked in a new wave of fighting since December 2005.

In India, security experts and officials agreed that the LTTE's action was a cause for concern, but were divided over a strategy to tackle the rebels.

"Whatever happens in the neighbourhood will affect India, directly or indirectly, sooner or later," D.R. Karthikeyan, a top security expert who probed the LTTE's 1991 assassination of former premier Rajiv Gandhi, told Times Now TV network.

"We have to impress upon the Sri Lankan government that peace is possible only when there is justice," he added, repeating international calls for a compromise in the long-running war.

Indian opposition leader Subramoniam Swamy, an outspoken critic of the Tigers, said New Delhi had to wake up to the LTTE's new military reach.

"The LTTE is not only operational in Sri Lanka: it has links with all terrorist groups in India," Swamy told reporters.

"I have maintained that we all in the region must have clarity, and that will come if we say the LTTE is part of the problem and not part of the solution," he said, pushing for a tougher Indian line against the rebels.