Zemari Bashary, the interior ministry spokesman, said the bomber had detonated his explosives when a policeman tried to stop him.

It was the second attack of the day, following a car bomb attack that killed at least two US soldiers in Zabul province.

Ghulam Sarwar, an Afghan army colonel, said that a suicide car bomber detonated his explosives outside a military base in the Shah Joy district of Zabul province.

There was no immediate claim of responsibility for either bombing.