Afghan police inspect the damage from an air strike on fuel tankers in northern Kunduz province on Friday that reportedly killed 70 people, including civilians. (Wahdat/Reuters) NATO has pledged to launch an investigation after it acknowledged civilians likely died in an air strike in northern Afghanistan that officials said killed at least 70 people.

NATO jets launched the air strike on Friday after two tankers transporting fuel to foreign forces were hijacked by Taliban militants near Omar Khel in Kunduz province.

The strike caused a huge blast that is believed to have killed at least 70 people, at least 45 of them militants, the local governor, Mohammad Omar, was quoted as saying.

He said Friday that as many as 90 people were killed, but later lowered the figure to 72 dead with 15 wounded.

NATO Secretary General Anders Fogh Rasmussen said civilians may be among the dead, but NATO is committed to protecting the Afghan people.

"It is a focal point for our ISAF troops to minimize the number of civilian casualties," he said, referring to NATO's 65,000-strong International Security Assistance Force.

Afghan soldiers removed human remains from the site and local residents were burying some of those killed in a nearby mass grave. Many of the bodies were burned beyond recognition, officials said.

"My brother was burnt when the aircraft bombed the fuel tankers. I don't know whether he is dead or alive," Ghulam Yahya, who was waiting outside the Kunduz hospital, told Reuters.

NATO commander Gen. Stanley McChrystal has ordered curbs on air strikes.

Afghan leaders have repeatedly criticized bombing campaigns, and called on NATO and U.S. forces to reduce the civilian death toll from their operations since they erode support for the international presence in the war-torn country.

Investigations launched

Wounded men are transported to hospital in Kunduz following the air strike. (Wahdat/Reuters)The United Nations released a report in August that indicates the number of civilians killed in conflict in Afghanistan has jumped 24 per cent so far this year, with bombings by insurgents and air strikes by international forces the biggest killers.

An Afghan investigation team has also been sent to the scene, said President Hamid Karzai's office in a written statement.

"No civilians must be harmed during military operations," the statement said. "Targeting civilians under no circumstances is acceptable."

The German military has troops under NATO command in Kunduz. Its commanders called in the air strike after the vehicles were seized near their base due to concerns about a possible suicide attack on the German base, Germany deputy Defence Minister Thomas Kossendey said Friday.

Officials said an unmanned surveillance aircraft was dispatched to the scene to determine there were no civilians in the area before an American jet conducted the air strike.

NATO had initially insisted the air strike was only launched after the fuel trucks were spotted surrounded by insurgents — with no civilians believed to be in the area.

But that statement was later toned down, with ISAF spokesman Brig. Gen. Eric Tremblay stating that "it would appear that many civilians causalities are being evacuated and treated in the local hospitals. There is perhaps a direct link with the incident that occurred around the two fuel trucks."

UN 'very concerned'

A Taliban spokesman told The Associated Press that the hijacked vehicles had become stuck in mud while trying to cross the Kunduz River. The valves had been opened to release the fuel and lighten the load and civilians had swarmed the area to siphon off the gas, he said.

Peter Galbraith, deputy chief of the UN mission in Kabul, said that he is "very concerned" by the reports of the civilian casualties.

Efforts must be undertaken to care for the wounded and compensate the families, Galbraith said.

"Steps must also be taken to examine what happened and why an air strike was employed in circumstances where it was hard to determine with certainty that civilians were not present," he said.

A UN team is being sent to Kunduz to participate in the investigation.

With files from The Associated Press