Technical problems — not hostile fire — brought the HH-60 helicopter down in Herat province late Wednesday, spokeswoman Lt. Col. Pam Keeton said. Two other airmen were injured, one of them critically, she said.
The election worker had been accidentally shot by a guard earlier in the day and the helicopter had been transporting him out for medical treatment. He suffered no further injuries in the crash.
Interim leader Hamid Karzai, meanwhile, appeared even more likely to win Afghanistan's landmark presidential poll with nearly two-thirds of the vote counted — but his margin looked slightly narrower as tallies rose for other candidates.
The Oct. 9 election, hoped to usher in peace after two decades of war, was a setback to Taliban rebels who failed to deliver on threats to derail the vote. Yet they continued to launch sporadic attacks in the lawless south and east of the country.
A homemade bomb destroyed two American Humvee vehicles in southeastern Paktika province near the Pakistan border, wounding three U.S. soldiers, one critically, and their Afghan interpreter, a U.S. military statement said.
All the wounded were taken to Camp Salerno, a U.S. military base in neighboring Khost province, for treatment.
Paktika Gov. Gulab Mungal said Afghan forces later arrested a suspect in the attack, whom he did not name, but identified as a deputy of Jalaluddin Haqqani, a front-line Taliban commander who served briefly as tribal affairs minister before the hardline Islamic regime fell in late 2001. He remains at large.
Mungal said several land mines, explosives and instructions on bomb-making, written in Arabic, were seized from the suspect's house.
There was no immediate claim of responsibility for the attack on the Americans, but Abdul Hakim Latifi, who claims to speak for the Taliban, vowed Thursday the rebels would continue their "holy war" against the U.S.-led coalition forces and the Afghan government.
"If the government holds elections 100 times this will not change the Taliban's commitment to jihad. The Taliban will pursue jihad until death," he told The Associated Press by satellite phone from an undisclosed location.
After the attack on the Americans, Afghan forces found three mines in the same area and defused them, he said.
The U.S. military, which has 18,000 soldiers hunting al Qaeda and Taliban rebels in eastern and southern Afghanistan, claims to have militants on the defensive after they failed to disrupt the country's Oct. 9 presidential election.
Still, about 1,000 people have died in political violence so far this year, including more than 30 U.S. soldiers. Many of the dead have been militant supporters of the Taliban, ousted from power in late 2001 by U.S.-led forces.