A car bomb struck a NATO military convoy in Afghanistan's southern city of Kandahar on Wednesday, causing several casualties, an AFP reporter said.
The powerful blast damaged an armoured vehicle, which appeared to belong to the Canadian military, and set a house alight, the reporter said.
A taxi driver named only Amanullah said he saw several bodies being carried off.
"I saw people with blood on their bodies rushed from the blast site. I don't know if they were alive or dead," he told AFP.
NATO's International Security Assistance Force (ISAF) and the Canadian military said they did not immediately have information about the attack.
Afghan officials could not be reached for confirmation.
Human flesh was scattered at the scene of the explosion, suggesting the blast was detonated by a suicide attacker, an AFP reporter said. Parts of the car used in the attack were flung around 100 metres (yards) away, he said.
Dozens of ambulances and police vehicles rushed to the site and Canadian troops blocked off the road, which is regularly used by the military to access the Kandahar Air Field, the main NATO base in southern Afghanistan.
Smoke was coming out of the damaged ISAF vehicle. Firefighters were trying to put out the house fire.
There was no immediate claim of responsibility for the attack but such blasts are usually carried out by the extremist Taliban, which was in government between 1996 and 2001.
The hardliners were ousted in a US-led campaign for not handing over their Al-Qaeda allies, wanted after the 9/11 attacks that killed about 3,000 people in the United States.
Kandahar city, capital of the restive Kandahar province from where the armed Taliban religious movement rose in the early 1990s, was the scene of the deadliest suicide bombing in Afghanistan.
The attack at a dog-fighting match on the outskirts of the city last month left about 100 people dead, although officials have said some were killed by gunfire from security guards who opened fire after the blast.
The blast killed a prominent anti-Taliban commander but the hardliners did not claim responsibility.