Kabul: A Taliban car bomber struck a NATO military convoy in the Afghan capital on Saturday, killing 17 people, including 13 US troops, in the latest in a string of major attacks to rock the war-torn nation.

The attacker blew up his Toyota sedan next to a US-run bus travelling through the southwest of Kabul at 1220 IST, raising tensions in the city already troubled by a spate of recent high-profile insurgent attacks.

The bombing was one of three deadly incidents for foreign forces across the country and comes as NATO prepares to hand large areas of Afghanistan to local forces and ahead of two international conferences aimed at bridging peace.

The Interior Ministry said three bystanders and a policeman were killed, while NATO's alliance force said at least 13 Western military forces died and US officials confirmed they were all  American.

"Initial reports indicate that 13 International Security Assistance Force (ISAF) service members died following an improvised explosive device attack in Kabul earlier today," the force said in a statement.

At least one other soldier was wounded in the massive explosion, US officials said, warning that the death toll could rise.

Thick black smoke could be seen rising from a fire still raging at the scene, cordoned off by Afghan and ISAF soldiers, while fire hoses were putting out another blaze nearby, footage on private television channel Tolo showed.

NATO's coalition forces were seen carrying the charred bodies of some of those killed away on stretchers from the wreckage of the bombed bus.

"It was a huge explosion, I saw at least 10 bodies of foreign forces taken out of their capsized bus and evacuated by two helicopters," one witness at the scene said.
Half a kilometre from the explosion, shattered windows and scattered pieces of twisted metal showed the scale of the massive blast.

The attack was the deadliest for the coalition since the death of 30 US troops, including 25 US Special Operations Forces, whose helicopter was shot down in mid-August south of Kabul in Wardak province.

Over the past few months a series of attacks in the capital have shown the resilience of the Taliban, more than ten years after the Islamist movement was toppled from power by a US-led invasion.

Eight other major incidents have hit Kabul since the beginning of the year, including a complex attack on a luxury hotel that killed 21 people in June, a deadly suicide bombing on a British cultural centre and a siege of the US embassy and NATO headquarters that killed at least 14 in a 19-hour siege.

The assassination last month of the government's chief peace broker, former President Burhanuddin Rabbani, also in Kabul, underscores the vulnerability of the capital as Western
governments look to withdraw their troops from the war.

A regional conference is to be held in Istanbul next week at which President Hamid Karzai is to give a list of areas in upto 17 provinces that will soon see a handover from NATO to Afghan control.

But there are deep doubts over the ability of the fledgling Afghan Army and police to secure the country, with the Taliban proving with recent attacks in the once-peaceful north of the country that they can strike anywhere.

In the volatile southern province of Uruzgan also Saturday, three Australian Army trainers were killed when an Afghan soldier turned his gun on them, NATO and Afghan Army
officials said.

In the eastern city of Asadabad in Kunar province, a female suicide bomber blew herself up outside a local branch of Afghanistan's spy agency, wounding two guards, a spokesman
for the Kunar provincial governor said.

The insurgent group claimed responsibility for the attacks in Kabul and Kunar.

"A suicide car bomb attack was carried out on a bus of foreign forces in the Dar-ul-Aman area of Kabul," said Taliban spokesman Zabiullah Mujahid in a text message sent.

At Kabul's Estiqlal hospital, 10 people had been brought in for treatment, but one policeman and one woman had since died of their injuries, said the head of the hospital Mohammad Ali Eshan.

One of the injured, 30-year-old Abdullah, who like many Afghans goes by just one name, had hurt his hands and face in the attack.

"I was driving my motorcycle, a convoy of foreign forces had stopped around 100 metres away. I suddenly heard a loud explosion and was knocked down," he said. "When I opened
my eyes I was in hospital."

The attacks come a day after the Taliban launched a four-hour long assault on a US-run civilian-military base and NDS local branch in the southern city of Kandahar, the spiritual birthplace of the insurgent movement.