At least 17 civilians were killed Monday morning in a suicide explosion launched by Tamil Tiger rebels in the no fire zone (NFZ) declared by the Sri Lankan government for war trapped civilians in the north, the military said.

The Ministry of Defense said in a statement that the attack happened when the troops tried to rescue about 10,000 civilians from the hands of the Liberation Tigers of Tamil Eelam (LTTE) in the less than 20-sq-km NFZ at Puttumatalan area.

Defense officials said the troops opened up a safe route for the civilians to come out of the NFZ after the soldiers captured 2. 5 km long stretch of LTTE built defense line at Puttumatalan, destroying the LTTE' ability to attack the civilians seeking refuge with the troops.

A pro-LTTE website said the Army began to deliver full fire- power against the NFZ at 2 a.m. (2030 GMT) and advanced into the zone at 11 a.m. (0530 GMT), causing heavy civilian casualties.

Actual number of civilians trapped in the NFZ is being debated. The government argued that only 120,000 people lived there, out of which nearly 70,000 have fled to government controlled area.

However, international agencies said more than 100,000 people are still being trapped in the NFZ.

A concerned international community has pleaded with both the government and the LTTE to care for the safety of civilians amid allegations that a large number of them are receiving injuries or getting killed in the crossfire.

More than 70,000 people have been killed in Sri Lanka's long drawn-out civil war since the mid-1980s when the LTTE began to rebel against the government based on claims that the minority Tamils were being discriminated in this Sinhamese dominated island.

Sri Lankan President Mahinda Rajapakse said recently that the remaining LTTE members "have only three alternatives. Either they have to surrender to our armed forces, eat the cyanide capsule and commit suicide, or plunge into the sea."