The LTTE confirmed on the Tamilnet.com website that two of their pilots, from their elite Black Air Tiger squad, were sent on Kamikaze-style attacks.
The website published a photograph of the two pilots together with Velupillai Prabhakaran, the LTTE leader.
The government claims it has encircled the separatists in under 100sq km of jungle in the north, but the attack shows the LTTE has the ability to strike far from the conflict zone.
Air defence activated
Thundering anti-aircraft guns erupted over Colombo's streets and tracer fire and spotlights lit up the skies, after one plane had been spotted on radar flying down the east coast.
Blackouts were ordered over parts of Colombo, which is heavily secured, and searchlights were pointed to the sky.
"Ground troops in the north of the island have seen two light aircraft heading towards Colombo," a military official said earlier.
"We have activated the air defence system," he said.
The LTTE has a small fleet of aircraft that it has previously used to carry out aerial attacks on Colombo.
Minelle Fernandez, Al Jazeera's correspondent in Colombo, said: "We have had since March 2007, when the LTTE launched its first air raid on Colombo ... a number of occasions when air raids have been launched, but they have not managed to hit any targets.
"Having said that, they have managed to come all the way to Colombo."
The Sri Lankan military claims to have put the LTTE under significant pressure since the start of the year, pinning the rebels back into an ever tighter area of the northeast of the island nation.
Rambukwella said that the military has destroyed or taken over six LTTE airstrips in the north east during their offensive, but that there could be a seventh one allowing the Tigers to launch the raid.
However, he said that the LTTE would be defeated.
"Right now we are very confident that this will come to an end," he said.
The LTTE has been fighting for a separate homeland for ethnic Tamils in the northeast of the country since the early 1980s.
Thousands have been killed in the conflict to date.