Afghan insurgents have captured two US soldiers south of Kabul, a Taliban official said this afternoon.
The NATO-led International Security Assistance Force (ISAF) had no official comment on the reported incident.
According to reports, local radio stations have broadcast US statements offering a $20,000 reward for information leading to their safe release.
"Early this morning two coalition personnel went missing. They are believed to have been captured by insurgents somewhere in Logar province," the broadcast said.
"They may have been separated from one another or maybe in the process of being moved to another location."
A Taliban spokesman said three ISAF servicemen had been captured but one had died. He did not elaborate.
The two US personnel were last seen wearing standard US military camouflage, the radio broadcast said.
"Coalition forces are offering $20,000 reward for any information that leads to the successful return of these two," the statement said, without identifying the men.
There is believed to be only one other ISAF soldier being held by the Taliban, who released a video of him last Christmas.
Violence in Afghanistan has risen sharply since a reinforcement brought to 150,000 the number of foreign forces facing the Taliban and two other insurgent groups.