A suicide car bomb exploded outside a NATO military base in Afghanistan on Monday, killing two Afghans, as US Marines pushed on with an assault against Taliban strongholds in the south.

The Taliban militia claimed responsibility for the suicide attack in southern Kandahar province and said its fighters had launched an "operation" to thwart the Marine push, now into its fifth day in neighbouring Helmand.

A minivan filled with explosives blew up about 30 metres from an outer entrance to Kandahar Air Field as it queued up at a checkpoint on a road into Kandahar city, an AFP reporter said.

Two civilians were killed and 11 people wounded, including two Afghan soldiers, commander of the army's southern corps, General Shair Mohammad Zazai, told AFP.

The air field, about 10 kilometres outside the city, is a vast complex that houses thousands of foreign troops including some reinforcements sent by US President Barack Obama as part of a sweeping new war strategy.

Zazai said the bomber was not targeting the base but was en route into the city, although police said his target was not clear.

Two vehicles trying to enter the military base were damaged — one carrying concrete barriers and the other loaded with armoured vehicles.

The NATO-led International Security Assistance Force confirmed the explosion but said its troops were not affected.

Taliban claims responsibility for attacks

Taliban spokesperson Yousuf Ahmadi claimed the attack on behalf of the insurgent organisation and said it was targeted at US soldiers. Taliban information is often incorrect or exaggerated.

The hardline Islamists have carried out a wave of suicide bombings in the last four years in a growing campaign seeking to bring down the US-backed government of Afghan President Hamid Karzai and kick out foreign troops.

The Kandahar air field is one of the biggest bases in Afghanistan for the tens of thousands of foreign soldiers deployed since the 2001 US-led invasion ousted the former Taliban regime.

Last week, about 4,000 US troops were airlifted into Taliban areas in Kandahar's adjacent Helmand province in one of the biggest operations over the last eight years and part of Washington's new strategy against the insurgency.

Their aim is to drive out the insurgents and establish security so Afghans can vote in presidential and provincial council elections on 20 August, a key test of a push towards democracy.

Ahmadi announced on Monday a new Taliban counter-offensive.

Foladi Jal, or "iron net" in Pashtu, would teach the Marines a lesson "so they will never again dare to come into our areas," he told AFP by telephone from an unknown location, threatening "mines and guerrilla attacks."

The Marines and about 650 Afghan forces have reported little resistance, except in one area where officers have reported days of heavy fighting with one Marine killed.

Taliban violence has been concentrated in the south but the insurgency has peaked this year, raising fears about the security of the August elections.

Separately, police said seven militants were killed in two days of operations by Afghan security forces against rebels in the southern province of Uruzgan.

The operation was launched after militants blocked a road to Kandahar by laying mines and massing there, said provincial police chief Juma Gul Hemat.

"The fighting is ongoing right now. So far, we have killed seven Taliban and two of our police have also been wounded," he told AFP.

AFP

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