NATO forces believed the three vehicles

Reporting from Kabul, Afghanistan - Swaying with the weight of their human cargo, two overloaded minibuses and a truck crept through a steep mountain pass, heading in the direction of Kandahar, the southern Afghan city the Taliban movement regards as its spiritual home. With an eye-in-the-sky view of the road and the surrounding terrain, NATO forces believed the three vehicles, closely trailing one another, were a convoy of insurgents preparing for an attack on coalition forces -- perhaps in neighboring Helmand province, where a huge offensive is underway, led by U.S. Marines. Afghan officials said they were innocent travelers, many of them women and children. Now at least 27 of them are dead and more than a dozen hurt, some severely, and the government of President Hamid Karzai is outraged -- all at a particularly delicate and potentially decisive moment in a battle for Afghan hearts and minds. The incident, the worst single episode of civilian casualties in six months, threatened to overshadow what coalition forces had billed as an important milestone in Marja: the first visit to the town by the newly appointed civilian chief, who will preside over a municipal government created essentially from scratch. Sunday's airstrike in Oruzgan province coincided with the war's biggest coalition offensive, centered on the town of Marja, in the Helmand River Valley. Both Helmand and Oruzgan provinces are part of a troubled arc of southern Afghanistan, one that will absorb the bulk of the 30,000 new U.S. troops President Obama has committed to the conflict. Militarily, the Western aim of the 10-day-old Marja campaign is to seize the town from insurgents who had made it their home turf for more than two years. But politically, the goal is to win over ordinary Afghans living in the Taliban heartland, bringing them around to the belief that order and governance will improve their lives in a way the insurgency leaders cannot. Western military officials said the Oruzgan airstrike was under investigation, an inquiry undertaken jointly by coalition and Afghan officials. But U.S. Army Gen. Stanley A. McChrystal, the commander of NATO forces in Afghanistan, immediately conveyed "sorrow and regret" to Karzai, a highly vocal critic of civilian casualties. In Washington, senior Defense Department officials also expressed regret, but avoided discussing details. "I would remind everyone of an essential truth: War is bloody and uneven," said Adm. Michael G. Mullen, chairman of the Joint Chiefs of Staff. "It's messy and ugly and incredibly wasteful, but that doesn't mean it isn't worth the cost." The day before the airstrike, Karzai, speaking to lawmakers, made an emotional appeal to foreign military forces to take greater care in keeping civilians out of harm's way. The North Atlantic Treaty Organization did not identify the nationality of the Western troops involved in the strike. U.S. Special Forces operate there, as in most provinces, but most of the soldiers serving there are from the Netherlands, which is set to pull out this year after a bitter political showdown over Afghan policy brought down the Dutch government on Saturday. Military officials said the Oruzgan strike was not connected to the Marja assault. But the sprawling offensive, involving 15,000 U.S., British and Afghan troops, has engendered a hair-trigger sensibility across much of Afghanistan's south, extending well beyond the immediate conflict zone. A statement from NATO's International Security Assistance Force confirmed that "airborne weapons" were used against the three vehicles in Oruzgan, in the belief that they carried insurgents. Arriving ground forces, however, found women and children, the military said. Afghanistan's Cabinet -- which condemned the attack as "unjustifiable" -- said at least 27 people died in the strike, including at least five women and children. A spokesman for Afghanistan's Interior Ministry, Zemari Bashary, said 14 people were hurt. In Marja, the arrival of Haji Zahir, a native of Helmand who has spent the last 15 years in exile in Germany, represented the first Afghan government presence in at least two years in the town, which had become the largest Taliban sanctuary in Helmand province. Insurgents had operated freely in Marja and its environs, turning the agricultural center into a hub of bomb making and narco-trafficking -- that is, until thousands of coalition troops, with U.S. Marines acting as the tip of the spear, launched a massive and much-publicized effort Feb. 13 to retake the town. In advance of the Marja campaign, Western commanders promised to take all possible measures to safeguard civilian lives. The Marines have been fighting under stringent new rules laid down last summer by McChrystal -- regulations so strict that troops on the ground believe they are putting their own lives on the line to follow them. Coalition troops are not supposed to fire on insurgents unless they are wielding a weapon or are observed discarding one. Buildings and homes -- even those being used as sniper posts -- are not to be fired on if there is a possibility that civilians are present, unless it is the only way to save troops' lives. Even with these precautions, NATO says at least 16 civilians have been accidentally killed by Western forces in the course of the Marja offensive -- 12 of them in rocket fire on a family home on the second day of fighting. That incident is under investigation as well. After days of intense clashes, Marja was quieter Monday, said Marine spokesman Capt. Abraham Sipe. The hazards were what has become the norm: buried bombs and sniper fire. "I don't know if it's a trend," said Sipe. "But it's good to see our Marines get a break, after so much firefighting."