Taliban insurgents on Saturday claimed they had shot down a military helicopter in eastern Afghanistan, killing 31 US special forces soldiers and seven Afghans in one of the worst single incidents involving foreign troops, according to dpa. NATO spokesman Tim James confirmed the crash, saying there was enemy activity where the helicopter went down. He refused to comment on whether it had been shot down. In a statement, the Taliban said "the helicopter was downed by a rocket-propelled grenade, and the wreckage of the chopper is still in the area." Citing a US official, who spoke on condition of anonymity because he was not authorized to speak to the media, the Washington Post reported that the helicopter was most likely struck by a rocket-propelled grenade. Most of the US dead were Navy SEALs, he said. Broadcaster CNN reported that the SEALs were on a mission to rescue another group of US troops who had been pinned down by enemy fire. None of the dead were from the SEAL team that killed Osama bin Laden in a May raid on the al-Qaeda leader's secret compound in Pakistan, CNN said. US President Barack Obama paid tribute to the US troops and their Afghan allies. The deaths were "a reminder of the extraordinary sacrifices made by the men and women of our military and their families," Obama said. "We also mourn the Afghans who died alongside our troops in pursuit of a more peaceful and hopeful future for their country," he said. NATO Secretary General Anders Fogh Rasmussen expressed sadness at the loss, stressing "NATO's strong solidarity with the American and the Afghan people as well as with their respective governments." "We are determined to stay the course, especially in this crucial period when Afghan and international security forces are working closer than ever to make transition a success," he said. Afghan President Hamid Karzai offered his "deep sympathies and condolences" to Obama and the families of dead. "The helicopter crashed Friday night in Maidan Wardak province and as result of the crash, 31 soldiers with US Special Forces, including crew members, were killed," Karzai said in announcing the news. He said seven Afghan soldiers were killed in the crash. Provincial Governor Mohammad Haleem Fedai said the helicopter crashed in the Tangy valley of Seyad Abad district. He could not confirm if it was shot down by the insurgents but said it was an insurgent-held area. "The Taliban activities are visible there," he said. Coalition and Afghan forces were conducting an operation against insurgents in the area and had killed eight Taliban, Fedai said, adding the coalition forces had cordoned off the area for investigation. A spokesman for the International Security Assistance Force (ISAF) said recovery operations were underway, and international forces were investigating the circumstances. Maidan Wardak is a volatile central province that borders Kabul. The deaths come two weeks after the start of handing over responsibility for security from foreign troops to Afghan forces, amid increasing security incidents and spreading violence. Aircraft crashes are relatively frequent in Afghanistan. There have been at least 15 coalition and Afghan aircraft crashes in Afghanistan since the start of this year. Most were attributed to mechanical failure or weather conditions. The crash appeared to be the deadliest in the 10-year Afghan war, exceeding the loss of 16 US troops in June 2005, when a Chinook was shot down by Taliban fire. In that incident in Konar province, near the Korengal Valley, a group of Army Rangers were on a mission to aid a team of Navy SEALs who had come under fire.