A land mine exploded under a vehicle south of Kabul on Saturday, killing four U.S. soldiers in the deadliest incident for American troops in Afghanistan in almost 10 months, the military said.
The explosion highlighted the dangers still facing foreign and Afghan troops more than three years after the fall of the Taliban, although there were conflicting accounts about whether the mine was freshly laid or left over from Afghanistan's long wars.
A Taliban spokesman claimed responsibility for the blast. However, U.S. spokeswoman Lt. Cindy Moore said investigators suspected the mine was an old charge dislodged by recent rain and snow or that the vehicle had wandered into an unmapped minefield.
"We believe it was an old mine which could have shifted," she said.
The victims were among a group of American and Afghan officials scouting a potential site for a shooting range in Logar Province, 25 miles south of the Afghan capital, when one of their three vehicles hit the mine, Moore said.
The bodies of the four dead were airlifted to the main U.S. base at Bagram, Moore said.
