The mother of a British aid worker who has been shown handcuffed on Russian TV said he was "not acting in his natural way" during the interview.
Paul Urey, 45, was one of two aid workers seized at a checkpoint in southeastern Ukraine last Monday, 25 April.
He was captured alongside his 22-year-old colleague Dylan Healy.
During the interview, Mr Urey claimed he wanted to visit Ukraine "to see if it was as bad as the news said" but it is not known if he was speaking under duress.
His mother, Linda, said: "I have watched the interview on Russian TV of my son Paul Urey.
"This is physically my son, but he is not acting in his natural way; his words are too matter of fact and his facial expressions make me not believe what he is saying. Normally he speaks fast and to the point.
"I know my son like every mother, and this is not him being natural."
'I told him not to go'
UK non-profit organisation Presidium Network said Mr Urey is a "family man with children" who didn't qualify for the army, so pursued work in the humanitarian sector.
Mr Urey last contacted the Presidium Network at 4am. Since then, they have received messages from someone claiming to be the volunteer, but who was unable to provide personal details to confirm their identity.
Ms Urey previously told Sky News his capture had left her feeling "like I want to die".
She said: "I don't know what to do anymore. It's horrible."
Ms Urey added: "I told him not to go. I said please don't go, he said: 'Mum, I can't live with myself knowing that people need my help to get to a safe place. I have to go'."
It comes after a British army veteran was killed and another British man went missing after they were believed to have travelled to Ukraine to fight against Russian forces.
Scott Sibley, 36, was confirmed as the first British national to have died in the war.
Injured Briton paraded on state TV
Andrew Hill has also been paraded on Russian state television after being captured by Russian forces, appearing with a bandaged left arm and a further bandage around his head.
He was filmed while being questioned, saying he had travelled to Ukraine of his own accord to help the country, Reuters reported.
Mr Hill signalled a connection with the International Legion, a unit set up by the Ukrainian government for foreigners who want to fight in support of the war effort.
Earlier this month, two British fighters, Shaun Pinner and Aiden Aslin, were captured by Moscow's forces.
The pair have been held in Ukraine and appeared on Russian state TV. They asked to be swapped for a Ukrainian politician who is close to Russian President Vladimir Putin.