KUNDUZ, Afghanistan, (Reuters) – A U.S. warplane  summoned by German troops fired on hijacked fuel trucks in  Afghanistan before dawn yesterday, killing as many as 90 people  in an incident that could trigger a backlash against NATO.

NATO initially said it believed the casualties were all  Taliban fighters, but later acknowledged that large numbers of  wounded civilians were being treated in hospitals in the area.

Villagers said their relatives were siphoning fuel from the  hijacked trucks and were burned alive in a giant fireball.  Patients arrived in hospitals completely covered with burns.

President Hamid Karzai’s office gave a death toll of 90. It  said he was deeply saddened and had sent investigators.

“No civilians must be harmed during military operations,”  Karzai said in a statement. “Targeting civilians under no  circumstances is acceptable.”

The incident, which took place in the northern province of  Kunduz, could reignite outrage against foreign troops two months  after the new U.S. and NATO commander in the country announced  measures to stop civilian deaths he says undermine the war.

Provincial officials, who themselves could face a backlash  over civilian deaths, said Taliban fighters were killed as well  as civilians. Provincial Governor Mohammad Omar said he believed  half of those killed were militants, while provincial police  chief Abdul Razzaq Yaqubi said 55 of the 90 dead were fighters.    Mohammad Sarwar, a tribal elder in the province, said  Taliban fighters had hijacked the tankers and were offering fuel  to a crowd of villagers when the tankers were bombed.

“We blame both the Taliban and the government,” he said.

Reuters reporters saw several young men with severe burns  arrive at the hospital by ambulance, where doctors said 13  people were being treated including three children.

Lieutenant-Commander Christine Sidenstricker, press officer  for the U.S. and NATO-led International Security Assistance  Force (ISAF), said Afghan authorities had reported two fuel  trucks hijacked. NATO aircraft spotted them on a river bank.

“After observing that only insurgents were in the area, the  local ISAF commander ordered air strikes which destroyed the  fuel trucks and killed a large number of insurgents,” she said.

ISAF spokesman Brigadier-General Eric Tremblay later said:  “It would appear that many civilian casualties are being  evacuated and treated in the local hospitals.”

A U.S. defence official said the strike was carried out by  an American F-15 jet. Germany’s Defence Ministry said permission  to fire had been granted by a German commander on the ground.

The strike took place near the border with Tajikistan, in a  part of the country once seen as safe but where Taliban attacks  have become increasingly frequent and fighters have asserted  control of remote areas. The Taliban consider fuel shipments a  strategic target because NATO forces depend on them.