Afghan authorities say a roadside bomb has killed two policemen in Herat province of western Afghanistan, just hours before a ceremony to hand a nearby police training academy over from NATO to Afghan control.

Raouf Ahmedi, a spokesman for the Afghan police commander for the western region, says one of the policemen killed in Saturday's explosion was a teacher at the academy in Adraskan district. He says two other policemen were injured by the remote-controlled bomb that exploded as their vehicle passed.

Last week, a bomb in a parked motorcycle exploded outside the training center, killing two security guards.

No one immediately claimed responsibility for the latest attack, but it matched the pattern of Taliban strikes that typically target Afghan forces and government workers.