Afghan officials said Monday that 52 people were killed in southern Afghanistan on Friday when a rocket fired by coalition forces slammed into a house where women and children had taken shelter from fighting between NATO troops and militants. But U.S. officials disputed the account. If the toll is accurate, the attack will be one of the worst cases of civilian casualties in the nine-year war. It comes as a leak of thousands of military documents Sunday casts new scrutiny on whether U.S. and coalition forces have taken enough care to avoid civilian deaths, and whether all of them have been reported by the military. The Afghan government said its information about the reported rocket attack, which took place in the Sangin district of Helmand province -- one of the deadliest areas for NATO troops in recent years -- originated with its own intelligence service, the National Directorate of Security. But late Monday, the U.S.-led military command in Kabul said that an investigation it was conducting with Afghan officials 'has thus far revealed no evidence of civilians injured or killed.' But it was not immediately clear whether the NATO investigative team had yet reached the scene. Interviewed by telephone, witnesses from the area where the attack was supposed to have taken place said that Friday a U.S. military force engaged Taliban militants in an intense firefight in two remote villages. Taliban fighters warned residents to leave. Many fled to Rigi, a remote village with only a half-dozen homes. Women and children from about eight families were packed into one home, while many of the men took shelter in the forest around the village, they said. About 4:30 p.m. they heard the first of two powerful explosions that blanketed Rigi in smoke as military aircraft flew overhead, the villagers said. One resident, Mohammed Usman, 57, said he helped pull the bodies of 17 children and seven women from the rubble. 'They have ruined us, and they have killed small children and innocent women,' he said. 'God will never forgive them.' Another resident, Abdul Samad, said: 'They targeted an area which we believed was safer, but in one hit they killed over 50 people. Most of them were children and women, and I have lost my relatives as well.' He said U.S. forces came to Rigi the next day and said they had fired because they had observed a man carrying a weapon. President Hamid Karzai condemned the attack as 'both morally and humanly unacceptable.' His government issued a statement saying 'success over terrorism does not come with fighting in Afghan villages but by targeting its sanctuaries and financial and ideological sources across the borders' -- a view he said was borne out by the leak of the military documents. But NATO military officials said the accounts of an attack were far from proved. 'Any speculation at this point of an alleged civilian casualty in Rigi village is completely unfounded,' said Rear Adm. Gregory J. Smith, director of communications for the U.S. and NATO military coalition. 'We are conducting a thorough joint investigation with our Afghan partners and will report any and all findings when known.' Another military spokesman, Lt. Col. Todd Breasseale, added, 'If the government of the Islamic Republic of Afghanistan has something that has been determined by means other than the joint Afghan/NATO investigation, we are unaware of it.' A senior U.S. military official also said there was frustration over Karzai's decision to issue the statement without coordination with NATO officials. 'It's not helpful to the relationship,' the official said. (BEGIN OPTIONAL TRIM.) In another skirmish six miles away, NATO said in a statement, attack helicopters had fired 'precision-guided missiles' at insurgents who had attacked troops with machine guns and rocket-propelled grenades. The missiles 'struck the intended target,' the statement said, killing six insurgents, including a Taliban commander. Initially, Afghan officials in Helmand said they were unaware of any attack on civilians. But Monday, Daoud Ahmadi, the provincial governor's spokesman, said officials had confirmed that the attack killed women and children, but he said he did not know how many. If the Afghan government's account is accurate, it would mean the largest number of civilians were killed in any attack since September, when more than 100 people died after a bomb strike called in by the German military in Kunduz province. The controversy could pose a challenge to the new U.S. and NATO commander, Gen. David H. Petraeus, just three weeks into his job. Last summer, Gen. Stanley A. McChrystal, then the U.S. commander of forces in Afghanistan, tightened the military's rules for using force, trying to avoid the civilian casualties that have enraged local populations and undercut support for the war effort among Afghans. The United Nations and other groups have praised the change, which reduced the number of deaths from airstrikes and night raids. But while senior military commanders have said they believe no troops have been denied close air support, McChrystal's directive has drawn strong criticism from many troops and families of service members who believed the new restrictions put soldiers and Marines at a disadvantage against Taliban insurgents. McChrystal was dismissed from his post for derogatory remarks he and members of his staff made about Obama administration officials and U.S. allies to a magazine reporter. His successor, Petraeus, has said he would weigh whether to loosen the rules again. But some military officials say they do not expect substantial changes. 