A road and air search was underway on Sunday for two American soldiers who went missing in eastern Afghanistan, with local radio stations offering a reward for their safe return.
The missing soldiers left their compound late on Friday "and did not return", a statement from NATO's International Security Assistance Force (ISAF) said, amid reports one of them may already be dead.
Their vehicle had been recovered in Logar province, south of Kabul, an official said on Saturday.
"Nobody has been found but there are reports that there may be a casualty and that the body has been removed from the scene," a military official said, speaking on condition of anonymity.
All reports were unsubstantiated, he added. ISAF said a road and air search had been launched.
A Taliban spokesman denied the insurgents were behind the disappearance of the soldiers, though earlier he had contacted media outlets with detailed descriptions of the soldiers and the equipment they were carrying.
Speaking to reporter by telephone from an undisclosed location, the Taliban's eastern Afghanistan spokesman, Zabihullah Mujahid, said, "So far, we are not aware of it and cannot confirm this".
A spokesman for Logar's provincial governor said the two soldiers left their base in Charkh district late on Friday "and went to opposition territory".
"One of them has been killed and the other has been detained by the opposition," Din Mohammad Darwaish said, referring to the Taliban.
A correspondent in Logar said two local radio stations had broadcast descriptions of the two missing men and offered a 10,000-dollar reward for information leading to their return.
The ISAF base at Charkh had told Logar media of the reward, with such details as the missing men's weight and moles on their skin, the correspondent said.
The ISAF official said their vehicle believed to be an armoured Toyota four-wheel-drive, had been recovered and that forensic tests would be carried out as part of investigations.
Kidnappings of foreign soldiers are rare in Afghanistan, where a nine-year insurgency has been escalating in recent months, particularly in the southern provinces of Helmand and Kandahar.
Most kidnappings in recent years have been by criminals for ransom, though targets identified as high value have in the past been sold on to insurgent groups, who then use them as political pawns.
A 24-year-old US soldier, Bowe Bergdahl, who disappeared on June 30, 2009 is believed to have been the first American snatched by militants in Afghanistan.
Bergdahl's captors have released at least two videos showing him to be alive, most recently in April.
The Taliban warned earlier this year they would target foreign military and government installations and staff, as well as Afghans working for them or for the Kabul government.
NATO said four US soldiers were killed by a bomb in southern Afghanistan on Saturday while a fifth American died in a later attack.
Both attacks involved improvised-explosive devices, or IEDs, the main weapon deployed by the Taliban in their insurgency.
The deaths bring to 397 the toll of foreign soldiers killed in the war so far in 2010, compared with 520 for all of 2009.
A tally based on that kept by the icasualties.org website puts the number of soldiers to have died since the Afghan insurgency began in 2001 at 1,965, with 1,205 of them Americans.
The US and NATO have almost 150,000 troops in Afghanistan, with the surge of an extra 30,000 Americans ordered by US President Barack Obama almost fully deployed, most of them in the hotspots of Kandahar and Helmand.
Washington's top military officer, Admiral Mike Mullen, was in Islamabad on Saturday amid US concerns about sanctuaries in Pakistan for extremist groups blamed for attacks on Afghan targets.
Mullen sought to dispel doubts in Pakistan about US "resolve" in the Afghan war, saying Washington remained committed to the fight against the Taliban.