The mother of one of two British aid workers who have reportedly been captured by Russian forces in Ukraine has said she feels "like I want to die".
UK non-profit organisation Presidium Network said Paul Urey, 45, and Dylan Healy, 22, were captured on Monday.
They are understood to have been seized at a checkpoint south of the city of Zaporizhzhia in southeastern Ukraine.
Mr Urey has been described as a "family man with children" who "didn't make the army" so decided to work in the humanitarian sector and travels lots.
Mr Urey's mother, Linda, told Sky News "he helps people who are in war" and had been in Ukraine for just over a week and a half but had travelled there before and returned recently.
She said she was left 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'."
She described him as "too caring" and said: "I wish he was a horrible person to be honest. And I know that sounds selfish, but you don't mess with the Russians. He's too kind."
She added: "I feel like I'm in my worst nightmare now.
"I just want them to give him back. He messaged me 20 times a day, he FaceTimes me nine times a day... nothing? Something's wrong. They've got him, definitely. He would contact me if he could, and he can't. I know he can't... And all he wanted to do was help people."
Meanwhile, Mr Healy was previously a kitchen manager at a hotel chain in the UK.
Presidium Network said the pair were working as volunteers and were known by the organisation but not linked to them.
It said the pair were working to evacuate a woman and two children from the region when they were captured at a Russian military checkpoint.
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.
Three hours after they were captured, the house of the woman who the pair were evacuating was stormed by Russian soldiers who made her husband lie on the floor and asked her how she "knew these British spies".
Dominik Byrne, one of the founders of the Presidium Network, said: "Our concern for these individuals is that the Russians will paint them as British spies which is untrue. They are civilian volunteers."
Ms Urey, Mr Urey's mother, said she last spoke to him on Monday morning when he told her he was "going to be going off radar" for 36 hours. She said she had since received a message saying "morning," and that he could not speak but would ring her.
She said "that was weird," and added: "He always says 'Mum' and he didn't say 'Mum'. He just said 'good morning,' he always says 'good morning Mum,' and I don't know if it was him."
Earlier International Trade Secretary Anne-Marie Trevelyan told Sky News the Foreign Office was "doing all it can to support" them.
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.
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 Viktor Medvedchuk, a Ukrainian politician who is close to Russian President Vladimir Putin.