At least 12 people have been killed and five wounded in a suicide attack at a police station in the southern Afghan province of Uruzgan, officials say.

Most of the victims are thought to be police officers who were having lunch at the time the attacker struck.

The station in Tirin Kot is used by police guarding the road to Kandahar.

A senior intelligence official told the BBC that the assailant had managed to gain entry to the dining hall because he was wearing a police uniform.

It was not clear if the bomber was a member of the police force, but Mohammed Khpalwak said it was a clear breach of security that would be investigated.

Five people were also injured in the incident. Some of the casualties were said to be friends and relatives of the police officers who had joined them for lunch.

Afghan police have consistently been targeted by the Taliban, and this attack comes shortly after Nato handed over security responsibility to local Afghan forces.

In a separate incident on Friday, two children were killed by a roadside bomb in the Chora district, officials said. They were thought to be aged 10 or 11.

A second suicide bomber also blew himself up at the Spin Boldak border crossing with Pakistan, killing at least two people and wounding several others. One report said a senior border police officer was among the dead.