Kabul: At least 10 people were killed and two dozen wounded on Wednesday when a fuel truck supplying one of the largest US-run bases in Afghanistan erupted in flames after being bombed, an official said.

A magnet bomb stuck on the side of the civilian-operated tanker blasted a hole in the fuel truck.

"When people gathered around it to collect the pooling fuel, a bigger explosion took place," said Parwan provincial spokeswoman Roshna Khalid, who confirmed the truck was bound for NATO base Bagram north of Kabul.

It was not clear what caused the second explosion.

"Ten people are dead and 25 others injured," Parwan governor Basir Salangi told AFP, condemning the attack as "an act of terror".

A Parwan hospital spokesman said it received three dead and 35 injured. Khalid initially gave a toll of 50 dead or wounded.

Mud graves were dug at the roadside for the dead as residents flocked to inspect the charred remains of the truck and the wreckage of several cars and motorbikes caught in the blast, a reporter at the scene said.

There was no immediate claim of responsibility. In northwest Pakistan, Taliban and other Islamist militants routinely blow up NATO tankers carrying fuel from the Arabian Sea to US-led troops in landlocked Afghanistan.

Parwan is expected to be part of a second wave of transition from NATO to Afghan control which President Hamid Karzai will announce at a regional conference in Istanbul on November 2.

Violence has increased in northern Afghanistan, but the region has been spared the worst fighting in the 10-year war, with most Taliban attacks concentrated on NATO and Afghan troops in the southern and eastern regions.