Hundreds of ethnic Tamils were removed from Sri Lanka’s capital over fears they could be a security threat, police said on Thursday — a move condemned by human rights campaigners as “ethnic cleansing”.

More than 300 Tamils were rounded up during a search for possible Tamil Tiger rebel infiltrators and were sent back to their home regions in the north and east by bus, said senior police officer Rohan Abeywardena. “We conducted a routine search operation and found these people were staying in Colombo without a valid reason,” he said.

Sirithunga Jayasuriya, chairman of the Civil Monitoring Committee that campaigns against human rights violations, said, “These Tamils have been denied their right to live in Colombo. Those who are involved in illegal activity should be arrested and punished through the court, but this is like ethnic cleansing and we strongly condemn it.”

The state has never before evicted an ethnic group from the capital because of security concerns. In 1983, the government provided ships to transport thousands of people to the north and east who were affected by an anti-Tamil riot in Colombo that intensified a separatist campaign by Tamil armed groups.

Tamil Tiger rebels forcibly evicted tens of thousands of ethnic Muslims, the country's second largest minority group, from the Tamil-majority Jaffna peninsula in 1990, alleging they were cooperating with security forces.

The government has previously said it does not deliberately target Tamils and that the routine searches are to improve security in Colombo, in view of two recent bomb blasts blamed on the rebels. On May 23, a bomb targeted a military bus, killing a soldier and wounding six others.