GHANZNI, Afghanistan (AFP) - A twin suicide attack, one of them a "massive" truck bombing, struck a US-run NATO base in Afghanistan's central province of Wardak on Saturday, killing at least six civilians, officials said.

Eight other people including two NATO soldiers were wounded in the attack around dawn, Afghan and NATO officials said.

"A suicide bomber on foot detonated near the gate of the base in Sayedabad, Wardak province, opening the way for a truck suicide bombing that followed him," provincial government spokesman Shahiddullah Shahid told AFP.

"Together they have killed six Afghan civilians, wounded four civilians and two intelligence personnel. There might be other casualties as well but I don't have information about them," he said.

A Western military official close to the NATO's International Security Assistance Force (ISAF) who spoke anonymously told AFP that only two ISAF soldiers were wounded in the blast.

"There were no ISAF fatalities," an ISAF spokesman told AFP separately, confirming the twin blast.

Sayedabad is an insurgency-plagued region and the base there was attacked by a truck bombing last September, exactly one year ago. More than 80 people, about 50 of them US soldiers, were wounded in that attack.

A witness said a small bazaar near the base, which is located along a highway that links capital Kabul to the southern province of Kandahar, was "totally destroyed" by Saturday's "huge explosion".

Afghan and Western troops blocked the road after the blasts for more than an hour, causing serious traffic-jams along the busy highway, the witness, who refused to give his name, told AFP. "They were huge explosions, very big," he said.

Many civilians work on or near NATO bases and bazaars.

Zabihullah Mujahed, a spokesman for the Taliban insurgents, claimed responsibility for the attack in a text message to AFP.

The United Nations says 1,145 civilians were killed and 1,954 wounded in the war in the first six months of this year, with the world body blaming 80 percent of the deaths on insurgents.

NATO has some 130,000 troops in Afghanistan fighting the Taliban's decade-long insurgency alongside government forces.

Most of the NATO troops are set to withdraw by the end of 2014 in a US-designed transition process that will put Afghan security forces in charge of security for their war-battered country.

The process is already underway with security responsibilities of about 50 percent of the Afghan population transferred to the local security forces. The United States invaded in Afghanistan in late 2001 in pace of 9/11 attacks on its cities.

Taliban have stepped up attacks in recent months with analysts saying could be aimed at undermining the transition process.