KABUL - A Taliban suicide bomber rammed an explosives-laden car into a NATO convoy in Kabul on Tuesday, triggering a massive blast that killed two Americans and one Polish soldier as well as wounding at least 13 civilians.
NATO troops gave first-aid to bloodstained comrades beside the wrecked remains of a military vehicle that was thrown to the side of the road, while city residents carried injured Afghans to hospital.
The attack was mounted during morning rush-hour traffic outside the Supreme Court and near the heavily-fortified US embassy, on a route used by NATO convoys every day.
A defence official in Washington confirmed two Americans had died but did not specify if they were soldiers or civilians, while an army spokesman in Warsaw said one Polish soldier had been killed.
One of the first people on the scene was Sayed Mustafa Saadat, 27, captain of the Afghan national rugby team, who was returning from an early morning training session.
"I rushed to help survivors. I picked up a local man who had a broken leg and was badly burnt," he told AFP.
"I carried him all the way to the hospital, running. It took about 10 minutes, but I don't know if he survived."
Kabul police spokesman Hashmat Stanakzai said at least 13 civilians were wounded and 17 cars were damaged by the suicide car bomb that shook buildings and sent a plume of smoke high above the city.
The NATO force has now 41,000 troops in Afghanistan, with about 29,000 from the US and just 300 from Poland.
All NATO combat soldiers will withdraw by December after 13 years of fighting the Taliban, with a follow-on mission of about 12,000 troops likely to stay on into 2015 on training and support duties.
The Taliban quickly claimed responsibility for the attack via a recognised Twitter account.
"(A) powerful explosion destroyed 1 military vehicle, killing/wounding a number of American terrorists," said Taliban spokesman Abdulqahar Balkhi.
Afghanistan is stuck in a political stalemate over election results, with the two presidential candidates in talks to resolve the prolonged dispute about who won the June 14 vote to replace President Hamid Karzai.
Ashraf Ghani and Abdullah Abdullah have been wrangling over a power-sharing deal after the vote was engulfed in allegations of fraud that have threatened to spark instability as NATO troops pull out.
Ghani, who is widely tipped to emerge as the new president, won the run-off election according to preliminary results, but Abdullah has consistently said he was the victim of state-backed ballot-rigging.
The standoff is clouding hopes that the US-led military and civilian aid effort since the fall of the Taliban regime in 2001 would leave Afghanistan as a democratic country.
With the government paralysed for months, it has also emboldened the Taliban insurgents, weakened the fragile economy and put future international military and aid support at risk.
Kabul has been regularly hit by complex Taliban attacks on the airport, luxury hotels, restaurants and foreign compounds, though there has a relative lull in recent months.
In August four civilians were killed in a similar attack on a NATO convoy in the city. No soldiers died in that blast, which wounded at least 35 bystanders.
Separately the International Security Assistance Force (ISAF) said one coalition soldier was shot dead on Monday by a man wearing an Afghan National Army uniform.
So-called "insider attacks" have undermined relations between foreign soldiers and the Afghan military, which is being trained to take on the Taliban alone after NATO's exit.