Nine suicide bombers have been killed along with four bystanders in an attack on government buildings in the Afghan city of Zaranj, officials say.

They say the bombers blew themselves up outside the governor's compound and a gun battle between insurgents and security forces lasted much of the day.

A Taliban spokesman confirmed to the Reuters news agency that the group carried out the attack.

Taliban militants are active in much of south-western Afghanistan.

The attack took place in Nimroz province - which has traditionally been seen as a Taliban stronghold, along with nearby Kandahar province.

Multiple fighters

Four people, including a provincial council member, two policemen and one civilian, were killed in the attack, the interior ministry said. Eight policemen and one civilian were wounded.

Officials say Afghan security forces fought with some of the attackers for more than two hours before the attack ended.

President Hamid Karzai's office said eight of the attackers had blown themselves up and police fatally shot the ninth.

Nimroz Governor Ghulam Dastagir Azad said that were at least seven explosions and that "police engaged with the attackers in five or six locations including the provincial council and provincial court".

The BBC's Martin Patience in Kabul says attacks using multiple fighters have become increasingly common in Afghanistan.

The latest incident comes only weeks ahead of a planned major military offensive in Kandahar province.

Nato and the US have deployed thousands of extra troops in Afghanistan, where numbers are due to peak at 150,000 in August under a strategy designed to bring a swift end to the conflict.