The Taliban say they captured a military dog from foreign forces operating in Afghanistan following a battle in the east of the country late last year.
In a video posted on the insurgents' website on Wednesday and later on Facebook, the Taliban claim the dog was seized from the US military.
But Western defence sources, speaking on condition of anonymity, said the dog belonged to British forces.
The video shows the animal, whom the Taliban said is named "Colonel", being held on a leash in a small, well-lit courtyard surrounded by five men holding guns and grenades.
Wearing a black vest with pouches for equipment, the dark brown canine wags its tail and later perks up its ears as the militants begin chanting "Allah hu Akbar" ("God is greatest").
A US defence official said the dog did not belong to the American military.
Britain's Ministry of Defence declined to comment.
The video's narrator says three rifles, one pistol, a GPS and a torch were seized together with the dog, after a military operation in Alingar, a volatile district in Afghanistan's Laghman province.
Taliban spokesman Zabiullah Mujahid said: "The Mujahideen put up fierce resistance and repelled the attack...
"The Mujahideen seized some weapons and also a dog which we later learnt the Americans called 'Colonel'."
The Taliban spokesman said Colonel is alive and well, adding that his fate would be determined later.
A spokesman for the NATO-led International Security Assistance Force in Kabul confirmed that a military dog had gone missing during a mission in December.
"We can confirm that a military working dog went missing following an ISAF mission in December, 2013. It is ISAF policy to defer identification to the appropriate national authorities," he said.
"Military working dogs are used for several purposes, primarily for explosives or drug detection."
Hundreds of canines have been deployed by international forces in Afghanistan for tasks such as seeking out improvised explosive devices responsible for the vast majority of both military and civilian casualties in the war-torn country.
The bravest among them are awarded medals and wounded animals are airlifted from the front line to be taken for treatment.
Dogs are seen as unclean creatures by some Muslims and viewed with suspicion by the Taliban.
