A suicide car bomber has killed at least 11 people in the eastern Afghan city of Khost, police say.
The attack, which targeted a police checkpoint in a crowded area of the city, left many wounded.
Police became suspicious and opened fire on the driver who blew himself up, provincial police chief Abdul-Hakim Isaqzai told the BBC.
The restive province, on the border with Pakistan, has long been a target for Taliban militants.
Mr Isaqzai told the BBC that nine civilians, three of them women, and two policemen had been killed in the attack.
"Many have been injured so the toll may go up," he said.
Reports said the blast sent a thick plume of black smoke into the air.
"It was very powerful. It shook Khost city," the Associated Press quoted the police chief as saying. He said security forces had surrounded the area and ambulances were taking the injured to hospital.
Police blamed the attack on Taliban militants who frequently target police checkpoints.
A suicide and gun attack on the police headquarters in the southern city of Kandahar on 12 February killed 19 people, including 15 policemen.
Violence has been on the increase in Afghanistan where tens of thousands of foreign troops are based.
Civilian and military casualties in Afghanistan are at levels not seen for a decade - last year more than 2,400 civilians died.
Nato says that gains made by Afghan and international troops are "tenuous and fragile" and has warned that there will be an increase in bloodshed this year.
In 2009, Khost was the scene of one of the worst attacks on US intelligence when eight people were killed by a suicide bomber at a CIA base.