Image caption The Kandahar attack left three police dead

At least 20 people, including 12 civilians, have been killed in four separate militant attacks in Afghanistan, officials say.

Women and children were among 10 killed when a minibus hit a roadside bomb in southern Helmand province.

Other bombings killed five Afghan soldiers in Laghman in the east, three police in Kandahar and two boys in Zabul province.

Militants frequently target security forces in Afghanistan.

'Militant haven'

Taliban insurgents have a strong presence in the volatile southern provinces of Kandahar and Helmand and have been leading attacks against Western forces and the Afghan government since they were ousted from power in 2001.

In the Helmand attack four women and two children were among the dead when their minibus - believed to have been to a wedding party - hit an improvised explosive device (IED) in Musa Qala. Six other people were wounded.

A spokesman for the Helmand governor blamed the explosion on the Taliban.

The five troops killed in Laghman were in a convoy hit by an IED in a remote area, officials said. Several others were injured.

They said that the convoy was travelling back from the volatile district of Badpakh after dropping off supplies.

Laghman has witnessed small-scale attacks by militants over the past year and correspondents say that the Taliban have increased their presence in rural areas of the province.

The province's relative proximity to Kabul and its mountainous, highly-forested valleys make it an attractive haven for militants.

In September, Nato-led forces killed eight women while conducting an operation targeting Taliban fighters in Laghman. Nato has since launched an investigation into the incident.

In the third incident, officials say a suicide bomber on a motorcycle attacked the outside of a police station in the city of Kandahar, killing three policemen and wounding two others.

They told the BBC that there could have been more casualties if the attacker had managed to get inside the busy station.

Elsewhere, a remote-controlled bomb in a bazaar in Zabul province killed two boys aged 12 and 14, officials said.

Nato combat troops are set to withdraw from the country by the end of 2014, handing over security responsibility to their Afghan colleagues.

The BBC's Bilal Sarwary in Kabul says that civilians continue to bear the brunt of the conflict and roadside bombs remain one of the biggest threats in rural parts of the country.