A bomb hidden in a parked motorcycle has exploded in Afghanistan's Garmsir district in Helmand, killing at least three people and wounding seven.

Omer Zawak, the spokesman for the provincial governor, said the explosion happened early on Tuesday at a weekly market in the village of Safar.

Safar is located 70km from the district centre of Garmsir, where anti-government fighters routinely stage deadly attacks.

A police spokesman, Shah Mahmood Hashna, said four children were among the wounded and two of them were in critical condition.

The explosion comes a day after three Georgian soldiers were killed in their base in Helmand in southern Afghanistan, when fighters detonated a vehicle laden with explosives, a senior Western military official and NATO said on Monday.

Elsewhere on Monday, in a separate incident, 10 civilians, mostly women and children, were killed when a roadside bomb hit the bus they were travelling in in Maroof district, roughly 60km northeast of Kandahar city.

Attacks by Taliban members have increased in recent months as the fighting season moves into high gear.