Gunmen ambushed and killed six US troops walking in the mountains of eastern Afghanistan - the most lethal attack of the year. The deaths made 2007 the deadliest for the US military here since the 2001 invasion, mirroring the record US toll in Iraq. The troops were returning from a meeting with village elders late Friday afternoon in Nuristan province when militants attacked with rocket-propelled grenades and gunfire. Three Afghan soldiers were killed and eight US troops wounded. "They were attacked from several enemy positions at the same time," Lt. Col. David Accetta, a spokesman for NATO's International Security Assistance Force and the US military, said Saturday. "It was a complex ambush." The six deaths brought the number of US troops killed in Afghanistan this year to at least 101, according to an Associated Press count, surpassing the 93 troops killed in 2005. About 87 died last year. The death toll echoes the situation in Iraq, where US military deaths this month surpassed 850, also a record. Both conflicts have seen an increase in troop levels this year that has put more soldiers in harm's way. Launched in the aftermath of the Sept. 11, 2001, terrorist attacks, the war in Afghanistan quickly ousted al-Qaida chief Osama bin Laden and his Taliban protectors and appeared to have been a swift military victory. But insurgent attacks - advanced ambushes and suicide and roadside bombs - have risen sharply the last two years, and analysts say the counterinsurgency battle US and NATO forces now face will take a decade or more to win. Violence is at record levels across the board. Insurgents have launched more than 130 suicide attacks, a record number, and Afghanistan last week saw its deadliest attack since 2001, a suicide bombing in Baghlan province that killed about 75 people, including 59 students and six members of parliament. More than 5,800 people, mostly militants, have died in insurgency-related violence this year, also a record, according to an AP count based on figures from Western and Afghan officials. The attack Friday was the deadliest incident for US troops since a Chinook crashed in February in Zabul province, killing eight Americans. Officials ruled out enemy fire as the cause of that crash.