Amid concerns over detention of hundreds of 'innocent' Tamils following last week's twin bombings in the Sri Lankan capital, President Mahinda Rajapakse on Monday assured that those not linked with rebels will be released.

At least 1,000 Tamils have been picked up by security forces for interrogation following Wednesday's blasts that killed around 20 people. The Liberation Tigers of Tamil Eelam is believed to have been behind the attack.

During a meeting with a group of eminent citizens, including a delegation of Ceylon Worker's Congress led by its leader and Cabinet Minister Arumugam Thondaman, Rajapakse said the detainees will be freed after authorities have finished checking their backgrounds.

The President also underlined the importance of the public support in the authorities' attempts to strengthen security. He also suggested the formation of Peace Committees in the capital and elsewhere.

"The President assured us that those, especially, in the upcountry areas will be released after a preliminary enquiry after scrutinising their documents," CWC spokesman R Yogarajan told PTI.

He said the President, however, said authorities will thoroughly interrogate those under suspicion of intelligence agencies.

Meanwhile, chief government whip and Highways and Road Development Minister Jeyaraj Fernandopulle on Monday told Parliament that suspects taken in for questioning on December 1-2 would be released after completion of investigations.

"The government has to take certain steps in the interest of National Security," the minister said.

"We are aware that 54 per cent of the Tamil-speaking people live in the South (of Colombo). All these security check-ups are in the interest of all communities. The forces have taken into custody over a thousand on suspicion. They will be freed after their identifications are established and above suspicion," he said.

Fernandopulle stressed that security forces have a duty to be vigilant, especially in areas where Tamil rebels are feared to be active.