RUSSIAN President Vladimir Putin claimed peace talks with Ukraine were at a “dead end” today, blaming what he said were “fake claims” by Kiev about war crimes.

A Ukrainian presidential spokesman said talks were ongoing, however.

The Russian leader spoke at a space centre in the country’s far east a day after the neonazi Azov Battalion, fighting in the besiged city of Mariupol, claimed its troops had been hit by a Russian chemical weapons attack.

A “poisonous substance of unknown origin” had affected three of its fighters, causing breathing difficulties and headaches, the former paramilitary unit, now part of the Ukrainian National Guard, said.

The Ukrainian government accused Russian forces of “firing on nitric acid tanks” in the Donetsk region based on information from local police. 

“Locals are urged to prepare protective face masks soaked in soda solution,” it advised. 

British armed forces minister James Heappey said today that “all possible options are on the table” if Russia had used chemical weapons. 

Pentagon spokesman John Kirby described the reports as “deeply concerning” while Ukrainian President Volodymyr Zelensky said that an oil embargo on Russia was essential. 

But Moscow denied involvement in a chemical attack, saying the accusation could be a pretext to draw other countries into the war. 

And chemical weapons expert Dan Kaszeta, a former US solider in the Chemical Corps, urged caution, saying that there remains “a paucity of information” about what took place in Mariupol.

He said that the symptoms described by the fascists could be explained by the inhalation of industrial fumes in what he described as “one big toxic burn pit.”

The fall of Mariuopol was feared to be imminent today as Ukrainian marines were among those surrendering to the Russians after 48 days of fighting. 

Aiden Aslin, a former care worker from Nottinghamshire who moved to Ukraine in 2018 having previously fought with the People’s Protection Units (YPG) against Isis in northern Syria, was one of them.

His family and friends denied claims he was a mercenary, saying he signed up for the Ukrainian military and holds dual Ukrainian and British citizenship. 

In a Twitter post, confirmed as genuine, Mr Aslin said: “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.”

In a voice recording, he said that there was no way out of the besieged city.