The pilot of a US military helicopter died after it crashed in western Afghanistan while two US soldiers on other side of the volatile nation were seriously wounded by a bomb, officials said. The Black Hawk helicopter came down near the city of Herat Thursday as it flew to rescue an electoral educator who had been accidentally shot by his armed escort, said UN spokesman Manoel de Almeida e Silva and US military spokeswoman Master Sergeant Wendy Frable. "One of the injured airmen died from his injuries," Frable told AFP. De Almeida e Silva told reporters the rescuers "were themselves victims of a helicopter accident". The pilot and two other US air force men were injured. The pilot succumbed to his injuries, the UN official said. An investigation was under way to determine the cause of the crash, according to another US military spokesperson, Captain Lindy White. Gunships and personnel carrier helicopters, along with A-10 attack aircraft are part of the US Air Force's contribution to the 18,000-strong US-led coalition hunting Taliban and Al-Qaeda fighters. Three US troops and their Afghan interpreter were injured by a bomb blast in the insurgency-hit southeastern province of Paktika Wednesday. "One soldier is in a critical condition, one in serious, and one in a stable condition. The interpreter is in a stable condition," a military statement said. Two US troops were killed in a similar attack last week in central Uruzgan province when a remote-controlled bomb blew up their vehicle. **PHOTO CAPTION*** A US Blackhawk helicopter lands. (AFP)