KABUL - A suicide car bomb targeting a U.S. military convoy in the Afghan capital Kabul killed two civilians on Tuesday, the latest attack to shake confidence in government efforts to uphold security.

While Afghan and foreign troops score tactical battlefield successes against the Taliban, strategic victory is still far from sight as insurgents launch more attacks over a wider area and Afghans grow ever more frustrated with a government seen as weak, corrupt and unable to keep the country safe.

The target of Tuesday's attack was a two-car convoy of U.S. troops outside a Defence Ministry building in the centre of Kabul close to embassies, and offices of the United Nations and World Bank.

All that was left of the bomber's car was the smouldering engine lying some 10 metres (yards) away from a metre-wide, burning crater in the road. Glass was shattered over a wide area and twisted shards of metal flew hundreds of metres away.

The blackened body of an Afghan civilian lay in the street covered with a prayer rug. Another Afghan, a security guard, was also killed by the explosion, a senior police official said.

"There was no one injured from our convoy," said Lieutenant Colonel David Johnson of the Combined Security Transition Command, which trains the Afghan army. "Our convoy was on a routine mission."

A spokesman for the Hizb-e Islami armed group of Afghan warlord Gulbuddin Hekmatyar claimed responsibility for the attack. While allied to the Taliban, Hizb-e Islami has carried out few, if any, suicide attacks.

HIT AND RUN

Afghan and foreign troops are engaged in daily hit-and-run battles with bands of rebels in the mainly Pashtun Taliban heartlands of the south and east, but suicide and roadside bombs in Kabul and the north show insurgents can now also strike areas seen as safe two years ago.

A dozen bomb attacks in and around the capital since June have killed 90 people.

A hard-line Islamist, Hekmatyar was one of the major mujahideen warlords fighting against the 1979-89 Soviet occupation and then led his fighters against other factions in a civil war that lasted until the Taliban captured Kabul in 1996.

Hekmatyar then fled to exile in Iran where he remained until after U.S.-led and Afghan forces overthrew the Taliban in the wake of the September 11, 2001 attacks on the United States.

The warlord returned to Afghanistan and allied himself with the Taliban to fight the Afghan government and foreign forces. Much smaller than the Taliban, Hizb-e Islami is active in a small patch of territory near the Pakistan border.

The Taliban has killed at least 200 civilians in around 140 suicide bombs this year in a campaign to overthrow the pro-Western Afghan government and eject the 50,000 foreign troops from the country.