Sri Lanka says it has shot down a Tamil Tiger plane - the first rebel aircraft to be brought down by the military.  As Anjana Pasricha reports from New Delhi, the government has also ordered aid workers out of the battle zone as fighting intensifies in the north of the country. 

Air force spokesman Janaka Nanayakkara says a small rebel plane was downed early Tuesday, hours after the Tamil Tigers, also known as the LTTE, launched an air and ground assault on a military base in the north.

"Once the aircraft came close to Vavuniya, the guns on the ground opened up, and the LTTE actually aircraft turned away and were in the process of returning, when our interceptors pursued them and one of these aircraft were shot down," Nanayakkara said.

It is the first time the air force has brought down a rebel plane since Tamil Tiger rebels surprised the military last year by mounting an air strike on a key military base near Colombo, demonstrating that they had air power. Since then, their planes - estimated to be just a handful of light aircraft - have struck at several targets, including a naval base two weeks ago.

If confirmed, the downing of the rebel aircraft would be another morale booster for the military, which has been making steady advances since it mounted a major offensive to crush the rebels.

The Defense Ministry says several rebels and soldiers were killed or wounded in Tuesday's fighting.

The new round of fighting came a day after the government ordered all aid workers out of the battle zone, saying it could not guarantee their safety.  Aid agencies have been helping an estimated 150,000 people displaced by the fighting.

The head of Colombo's National Peace Council, Jehan Perera, says the government's order may be meant to protect aid workers.  He says it may also be meant to ensure that there are no "witnesses," if civilians are killed during the military offensive. 

"If there are civilian casualties, then there will be international outcry against that offensive, which the government may wish to reduce by asking aid workers to leave," Perera said.

Rights groups have accused both government forces and rebels of disregarding the safety of civilians in the course of the war.  They have also blamed them for murder and abduction of civilians.

The rebels have been fighting for a quarter of a century for an independent homeland for the Tamil community.  The government says it is confident of ending the long-running insurgency by the end of the year.  Analysts are skeptical.