British man is feared among those surrendering to Russian troops as resistance collapses in the besieged port city of Mariupol.
Aiden Aslin, 27, told friends that he had run out of food and ammunition while defending the city.
Mr Aslin, from Newark, Nottinghamshire, is a member of the 39th Brigade Ukrainian Marines having taken an oath to defend Ukraine after completing training in 2018.
The former care worker Mr Aslin, passed on a message to his followers through a friend, tweeting: “It’s been 48 days. We tried our best to defend Mariupol but we have no choice but to surrender to Russian forces.
“We have no food and no ammunition. It’s been a pleasure everyone, I hope this war ends soon.”
The fighter, who was due to get married this month, has been keeping his followers up to date over social media.
He called for the West to bring an end to Putin’s “civilian bombing” campaign.
In his latest selfie video, he confirmed he was still alive in the war-torn city of Mariupol.
A friend added on a Instagram page: “He said he loves you all. He is strong in spirit and showed no weakness at all. He is surrendering to Russians which is only slightly better than surrendering to the Chechens.
“Their commander will be meeting them soon. Please Lord have mercy.”
It came as Vladimir Putin was warned on Tuesday that “all possible options are on the table” about how the West would respond to his use of chemical weapons amid claims that such an attack has already been launched in Mariupol.
More than 10,000 civilians have died in Mariupol and their corpses have been “carpeted through the streets”, the city’s mayor has said on Monday.
Mayor Vadym Boychenko made further claims the full death toll could surpass 20,000 – twice the number he has already claimed to have died.
The mayor also said Russian forces have taken many bodies to a huge shopping centre where there are storage facilities and refrigerators.
“Mobile crematoriums have arrived in the form of trucks: You open it, and there is a pipe inside and these bodies are burned,” he told The Associated Press by phone.