The U.S. commander in Afghanistan will soon order U.S. and NATO forces to break away from fights with militants hiding among villagers, an official said Monday, announcing one of the strongest measures yet to protect Afghan civilians.

The most contentious civilian casualty cases in recent years occurred during battles in Afghan villages when U.S. airstrikes aimed at militants also killed civilians. American commanders say such deaths hurt their mission because they turn average Afghans against the government and international forces.

Afghan President Hamid Karzai has pressed U.S. forces for years to reduce civilian casualties, but his pleas have done little to stem the problem. The U.N. says U.S., NATO and Afghan forces killed 829 civilians in the Afghan war last year.

Gen. Stanley McChrystal, who took command of international forces in Afghanistan this month, has said his measure of effectiveness will be the "number of Afghans shielded from violence" — not the number of militants killed.

McChrystal will issue orders within days saying troops may attack insurgents hiding in Afghan houses if U.S. or NATO forces are in imminent danger, said U.S. military spokesman Rear Adm. Greg Smith.

"But if there is a compound they're taking fire from and they can remove themselves from the area safely, without any undue danger to the forces, then that's the option they should take," Smith said. "Because in these compounds we know there are often civilians kept captive by the Taliban."

McChrystal's predecessor, Gen. David McKiernan, issued rules last fall that told commanders to set conditions "to minimize the need to resort to deadly force."

But McChrystal's orders will be more precise and have stronger language ordering forces to break off from battles, Smith said. The order should have the effect of reducing the use of airstrikes, mortars and artillery in villages.

McChrystal, who took command one week ago, has already given the order to commanders in northern and eastern Afghanistan he has met with. The four-star general will meet with commanders in the south and west in coming days. Soon after the visits are completed, the new directive will be formalized, Smith said.

In the most recent civilian deaths case, a May 4-5 battle between U.S. and Afghan forces and militants in western Farah province killed dozens of civilians. A U.S. report last week said U.S. forces killed an estimated 26 civilians. However, Karzai's government says 140 were killed, while an Afghan human rights group says the number is about 100.

"This new policy shows that they've really taken on board the fact of the matter in Afghanistan — that you lose the war if you lose the people," said Sarah Holewinski, the executive director of the Washington-based Campaign for Innocent Victims in Conflict. "I was heartened by McChrystal's remarks last week stating that, and am now further heartened to see that he's backing those statements up with policies to protect civilians. This is what we've wanted all along."

Still, she said the policy has potential drawbacks, specifically that once Taliban fighters learn of the directive, civilian homes will be the perfect place to seek cover.

Holewinski noted the policy will still allow troops to use airstrikes when they are in danger.

Smith said McChrystal will address in the coming months how U.S. and NATO forces are deployed around the country, and forces could be withdrawn from remote regions in order to concentrate troops around population centers.

In the latest violence, a suicide bomber on a motorbike killed seven civilians Monday when he drove into the center of an eastern Afghan city and set off explosives.

The bomber detonated explosives on his motorbike in front of Khost city's electric power headquarters and then explosives on his body a few minutes later, said Kuchi Naseri, a spokesman for the governor of Khost province. The Interior Ministry said seven people were killed.

The target of the attack was unclear. There were no military or police nearby, Naseri said, but the later blast may have been planned to hit police or officials rushing to the scene. Another 30 people in the area were wounded, he said.

In southern Kandahar province, another suicide bomber killed three Afghan soldiers in an attack on a convoy of troops inspecting a highway bridge for explosives, said Zadi district Police Chief Niaz Mohammad Serhadi.

In eastern Nangarhar province, an explosion at a weapons cache killed a 6-year-old boy and wounded 20 others, police said.