THIRTEEN AMERICAN TROOPS have been killed in Afghanistan after a Taliban suicide bomber rammed a van into an armoured NATO bus. Four Afghans were also killed in the blast.

The explosion occurred as the convoy was passing the American University, sparked a fireball and littered the street with shrapnel. Heavy black smoke poured from burning wreckage at the site.

The armored personnel carrier, known as a Rhino was sandwiched between of a convoy of mine-resistant military vehicles traveling on a four-lane highway frequently used by NATO forces in a southwestern section of the city.

NATO said 13 service members were killed, but a U.S. official confirmed they were all Americans.

The Afghan Ministry of Interior said three Afghan civilians and one policeman also died in the attack. Eight other Afghans, including two children and four other civilians, were wounded, said Kabir Amiri, head of Kabul hospitals. The New York Times reports that a military dog was also killed.

According to the BBC such attacks are rare in Kabul, which is heavily-guarded.

The Taliban claimed responsibility for the Kabul attack, sending a text message to media outlets. The Taliban also claimed responsibility for another suicide bombing outside a government intelligence office in the northwest province of Kunar.

NATO and Afghan forces sealed off the area as fire trucks and ambulances rushed in. An Associated Press reporter at the scene saw two NATO helicopters landing to airlift casualties, while coalition troops using loudspeakers ordered bystanders to evacuate the area.

It was the deadliest single attack against the U.S.-led coalition since the Taliban shot down a NATO helicopter on 6 August in an eastern Afghan province, killing 30 U.S. troops, most elite Navy SEALs, and eight Afghans.

In other violence, a man wearing an Afghan military uniform opened fire on a joint NATO-Afghan base, killing three NATO service members in Uruzgan province, an area in the restive south that is traditionally viewed as the Taliban’s stronghold.

Afghan Defense Ministry spokesman Mohammad Zahir Azimi said officials were investigating whether the shooter, who was killed in the incident, was a member of the Afghan army or a militant wearing an army uniform.

- Additional reporting by AP