Three civilians were killed and another 25 were wounded when a bomb fixed to a bicycle exploded on Saturday in eastern Afghanistan, the governor said.
The explosion happened in a crowded area in Mihtarlam city, the capital of Laghman province, east of the capital, Kabul, the acting provincial governor Murtaza Qalandarzai said.
"Three civilians were killed and another 25 were wounded in the blast," he said, adding that a child and a woman were among the dead.
The target of the blast was not immediately clear. The bicycle was left some 50 metres (yards) from a police checkpoint, with no military or government installations nearby.
Homemade bombs or improvised explosive devices have become the weapon of choice for Taliban insurgents and are responsible for most fatalities and casualties among Afghan and NATO troops as well as civilians.
Last Saturday, explosives attached to a motorbike killed 10 civilians in a market in a remote town in northern Kunduz province. The target of the attack - a pro-government militia leader - was also killed.
This week, a group of 29 domestic and international aid agencies urged NATO leaders meeting in Lisbon to do more to protect civilians, as they discuss the timetable for the handover of security powers to Afghan forces.
This year is the deadliest year for civilian casualties in Afghanistan, according to the United Nations.
The number of ordinary Afghans killed in the conflict rose by a third in the first six months of 2010 to 1,271, with most deaths caused by insurgent attacks, the world body said in its six-monthly update in August.