The top NATO commander in Afghanistan said Saturday that local villagers were among those wounded at the site of an airstrike on hijacked fuel tankers, declaring his resolve to limit civilian casualties that threaten to undermine the war against the Taliban.

U.S. Gen. Stanley McChrystal inspected the spot where a U.S. fighter jet blasted the hijacked tankers early Friday, killing as many as 70 people. The pre-dawn strike occurred despite McChrystal's new orders restricting the use of airpower if civilian lives are at risk.

McChrystal also visited a hospital Saturday where the wounded were taken, stooping low to talk with a 10-year-old boy with severe burns, his arms and legs swathed in gauze.

Local officials have said scores of people died in the fiery blast, but it was unclear how many were militants and how many were villagers who rushed to the scene to siphon fuel from the stolen trucks. A NATO team began an official investigation Saturday amid a clamor from European leaders for answers, with some calling the airstrike a "tragedy" and "a big mistake" that must be investigated.

"From what I have seen today and going to the hospital, it's clear to me that there were some civilians that were harmed at the site," McChrystal told reporters in Kunduz. He did not say if any civilians were killed.

McChrystal waded through knee-high water to view the blackened NATO tankers, which exploded when a U.S. F-15E Strike Eagle jet dropped two 500-pound (225-kilogram) bombs on them a few miles (kilometers) outside the main town in northern Kunduz province.

Reporters traveling with him saw about a dozen small yellow fuel cans had survived the blasts. Several were still full of fuel.

Before traveling to the site of the bombing, McChrystal met Afghan leaders in the provincial capital. He expressed sympathy for any civilian losses and said the fight against the Taliban should not come at the expense of civilian lives.

"I am here today to ensure that we are operating in a way that is truly protecting the Afghan people from all threats," McChrystal said.

At least one local official supported the allied bombing, saying it would help drive the insurgents from the area.

"If we did three more operations like we did yesterday morning, the Kunduz situation would be peaceful and stable," said Ahmadullah Wardak, a provincial council chief.

McChrystal discussed the incident with Afghan President Hamid Karzai and later told senior commanders that "we need to know what we are hitting," an aide said, speaking on condition of anonymity under command policy.

The NATO investigative team flew over the site on the Kunduz River where the U.S. jet, called in by the German military, bombed the tankers, which reportedly became stuck trying to cross a river. German officials have said the Taliban may have been planning a suicide attack on the military's nearby Kunduz base using the tankers, which were hijacked carrying NATO fuel supplies from neighboring Tajikistan.

The team led by U.S. Rear Admiral Gregory J. Smith, NATO's director of communications in Kabul, also spoke to two wounded villagers in the Kunduz hospital, including a boy and a farmer with shrapnel wounds.

Mohammad Shafi, 10, who was injured in the blast, told Smith from his hospital bed in Kunduz town his father told him not to go near the stolen tankers, but he went anyway. "While I was going to get the fuel, on the way I heard a big bang, and after that I don't know what happened," he said with bandages on his arm and leg.

Local government spokesman Mohammad Yawar estimated more than 70 people were killed, at least 45 of them militants. Investigators were trying to account for the others, he said.

Germany said 57 fighters were killed in Friday's airstrike and no civilians were believed in the area at the time, based on surveillance of the tankers by a drone aircraft. NATO Secretary-General Anders Fogh Rasmussen, however, acknowledged some civilians may have died, and the U.S.-led coalition and the Afghan government announced a joint investigation.

European leaders called Saturday for a speedy investigation. French Foreign Minister Bernard Kouchner called the airstrike "a big mistake," though he said he was not blaming anyone until the probe is complete. EU External Relations Commissioner Benita Ferrero-Waldner called the incident "a great, great tragedy."

German Defense Minister Franz Josef Jung insisted in comments to the Bild am Sonntag weekly that officials had no information indicating any civilians were killed in the airstrike.

"Based on the information I have at this time, only Taliban terrorists were killed in the strikes carried out by U.S. aircraft," Jung was quoted as saying.

The deputy U.N. representative to Afghanistan, Peter Galbraith, said Saturday he was "very concerned" about the reports of civilian deaths.

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

NATO said two U.S. service members died in Afghanistan on Saturday. One died of wounds after coming under fire in eastern Afghanistan, while the other was killed by hostile small-arms fire in the west, statements said.

A Polish soldier was killed and five others were wounded by a roadside bomb in eastern Afghanistan, Poland's Defense Ministry said Saturday. The incident occurred when the bomb exploded under their armored vehicle Friday.

A bomb blast hit a German military convoy Saturday in Kunduz, damaging at least one vehicle and wounding four troops, none seriously. The more than 1,000 German troops in Kunduz have come under increasing militant attack in a region that had largely escaped the scale of violence seen in the east and south of Afghanistan.