Three policemen were killed and six injured Thursday when a bomb exploded on a bus in eastern Afghanistan, an official said, DPA reported.
The policemen were travelling from Jalalabad, the capital of Nangarhar province, to a nearby police academy, said Ahmad Zia Abdulzai, spokesman for the province's governor.
Taliban insurgents, who have been fighting a bloody insurgency since their ouster from power in 2001, have been increasingly targeting Afghan security forces in recent weeks.
On Friday, the police chief in the volatile southern province of Kandahar was killed in a suicide attack inside his headquarters.
A day later, another suicide bomber struck an army base in the east of the country, killing five US soldiers, four Afghan officials and a translator.
On Monday, a suicide bomber gained access to the Defence Ministry in Kabul, killing three soldiers before he was shot and killed.