Four policemen and the woman bomber were killed Wednesday in the first suicide attack in Colombo since the Sri Lankan government and the Liberation Tigers of Tamil Eelam (LTTE) reached a truce in February 2002.

"Although no one has claimed responsibility for the bombing, the incident bears the hallmarks of an LTTE attack," the US embassy said in a statement.

"The US has consistently called on the Tigers to renounce terrorism and cease terrorist acts, including political assassinations, and to comply with the terms of the ceasefire agreement that they signed," the embassy said.

The United States said it would not lift its October 1997 ban on the Tigers as a terrorist group until the rebels completely renounced the use of violence and entered the democratic mainstream.

Officials said the suicide attack was aimed at Douglas Devananda, a Tamil government minister who fiercely opposes the LTTE's campaign to set up a separate homeland for the minority.

Police said Friday they arrested a woman accomplice of the suicide bomber. The 29-year-old woman, who was remanded in custody, had earlier worked for Devananda, police said.

"This woman had been tasked with taking the suicide bomber up to minister Devananda's office," a police spokesman said. "But security guards did not allow her (the bomber) in without subjecting her to a body search."