Sri Lanka's military says a roadside bomb has killed six police officers and a civilian in the east of the country.

A military spokesman, Prasad Samarasinghe, says Tamil rebels are suspected of triggering the blast in Batticaloa district. Sri Lankan security forces captured a main rebel base in Batticaloa earlier this month.

Wednesday's explosion hit a police bus as it was carrying officers home on leave. One civilian passerby was killed, and several police officers were wounded.

No group has claimed responsibility for the bombing. Roadside bombs are often used by Tamil rebels in their attacks on Sri Lankan security forces.

Fighting between the rebels and government troops has escalated in recent months, despite a 2002 truce.

Sri Lanka's government has vowed to wipe out the Tamil rebels militarily.

On Monday, U.S. Ambassador to Sri Lanka Robert Blake said a military solution to the conflict is not possible, and he urged both sides to reach a power-sharing agreement.

Some information for this report was provided by AFP, AP and Reuters.