Media playback is unsupported on your device Media caption BBC Persian's Kawoon Khamoosh who witnessed the attack says it took place at the busiest time of the day

At least three coalition personnel have died after a Taliban suicide car bomber rammed into a foreign military convoy in the Afghan capital Kabul, Nato says.

The blast killed a Polish soldier and two Americans serving with Nato. A fourth member of the Nato force was seriously injured.

At least 16 civilians were also hurt, Afghan government sources say.

The blast took place in heavy traffic on the airport road near the US embassy at about 08:00 local time (03:30 GMT).

The blast comes amid uncertainty over disputed presidential elections and the withdrawal of most Nato troops by 2015.

A statement from the Nato-led coalition confirmed that three International Security Assistance Force (Isaf) members died in the attack.

Blood-stained soldiers

The BBC's David Loyn in Kabul said the three Nato members were travelling in an armoured vehicle, which was destroyed in the blast.

Our correspondent says the explosion shook buildings across the centre of the capital.

The AFP news agency reported that foreign troops were seen giving first aid to blood-stained soldiers from the convoy.

Image copyright AFP Image caption People at the scene carried those injured in the attack to hospital

Image copyright AFP Image caption The explosion reportedly shook buildings across the centre of Kabul

BBC Persian's Kawoon Khamoosh in Kabul says nearby buildings and cars were hit with broken glass.

Eyewitness, Ahmad Ajmal, told the Associated Press news agency: "When I got out of the vehicle and started walking, an explosion happened, the same vehicle I was in is there and destroyed."

Taliban sources told reporters via e-mail and on Twitter that the group had carried out the attack.

Meanwhile, Isaf said another Nato member was killed "as a result of an individual wearing an Afghan National Army uniform turning his weapon against Isaf members" on Monday.

The incident took place in Herat, west Afghanistan. A western official, speaking on condition of anonymity, told Reuters news agency that the Afghan man had thrown a grenade at his trainers.

Disputed election

The two candidates vying for Afghanistan's presidency, Ashraf Ghani and Abdullah Abdullah, have been locked in a dispute over the results of the recent election, which was rocked by allegations of fraud.

Image copyright EPA Image caption Negotiations between Ashraf Ghani (pictured) and Abdullah Abdullah have caused uncertainty

Image copyright AP Image caption Abdullah Abdullah (pictured) and Ashraf Ghani held talks on Monday on how to end the political deadlock

The two are now negotiating a power-sharing deal and met on Monday to discuss it.

Correspondents say that Taliban insurgents have taken advantage of uncertainty over the presidential election to launch attacks.

In July a Taliban suicide bomber killed four people, including at least three foreign security guards, in an attack on a key counter-narcotics building outside Kabul airport.

That attack came days after security forces repelled an attack on Kabul airport by the Taliban.

Mr Abdullah himself was targeted by a suicide bomb attack in June, also in Kabul. Six people were killed and at least 22 injured when two blasts hit a rally. He survived unscathed.