Twelve people were killed and more than 80 wounded when Taliban fighters detonated two car bombs at a gate outside police headquarters in the Afghan city of Kandahar today, police and medical officials and the Taliban said.

After the blasts, militant gunman opened fire from nearby positions and members of the security forces were battling them, said Tadeen Khan, the southern city's chief of police.

The attackers targeted the police force's counter-narcotics wing, Khan said.

Eyewitnesses said that following the first explosion, three back-to-back explosions were heard and the gunfight was still going on.

Police cordoned off the area as passers-by fled.

Those killed were both policemen and civilians, said Bahir Ahmadi, a spokesman for the provincial governor, giving the death toll.

A doctor on duty in Kandahar provincial hospital said 83 wounded people had been taken to the hospital, most of them civilians.

The Taliban said in a statement their fighters had detonated car bombs and clashes were continuing as some fighters had entered the police offices.

Kandahar was the former seat of the Taliban when they ruled Afghanistan from 1996 until they were ousted by a US-led coalition in 2001.

The militants have fought on and while US officials and Taliban militants have been discussing a peace deal since late last year to end the war, the violence has not abated.

At least 20 Afghan forces members were killed in a Taliban ambush in Abkamari district in western Badghis province on Wednesday.

The Taliban also killed an Afghan commander on Wednesday in central Afghanistan. Mateen Mujtaba, who headed an army division in Ghazni province, was conducting a security check in Qarabagh district when an Afghan soldier started shooting.

Officials said the soldier was an infiltrator of the hardline Islamist group.