At least 13 people have been killed and 20 others injured after a suicide bomber hit a minibus carrying police cadets in eastern Afghanistan, a government spokesman has said.

The attack took place at around 4:45 pm (1215 GMT) in the eastern province of Nangarhar, just outside the city of Jalalabad.

Ahmadzia Abdulzai, a spokesman for the governor of Nangarhar province, said a suicide bomber drove an explosives-packed car into the bus carrying the cadets.

"It was a suicide attack against a small bus carrying Afghan police," Abdulzai told Reuters news agency.

"The dead and wounded include police and civilians."