The UK’s independent reviewer of terrorism has told of the dangers of British extremists using the Ukraine crisis to fight for the far-right Azov Battalion group.
Jonathan Hall QC has raised awareness of the issue as the UK's Foreign Secretary Liz Truss said she would support UK citizens who wanted to volunteer to help Ukraine.
Ukraine's president, Volodymyr Zelenskyy, on Sunday asked foreign volunteers to come forward and offer their assistance, promising them arms to fight as he announced the formation of a new “international legion” to help defend his country.
The situation had intensified on Tuesday after it was reported a 64-kilometre Russian convoy of tanks and artillery was advancing on Kiev, Ukraine's capital.
Mr Hall said that while travelling to Ukraine and taking up arms might appear “attractive”, it could open a gateway to extremists fighting for far-right groups.
"Russia's aggression against international legal order and the importance of supporting Ukraine makes support for foreign fighters who want to travel to Ukraine at first glance attractive," he said.
“Given the government's apparent support, prosecution of foreign fighters against Russia under terrorism legislation appears to be a non-starter, even if the broad statutory definition of terrorism is satisfied in these cases.
“But there is always the possibility of less desirable cases at the edges – individuals who travel to Ukraine under false pretence either to support Russia or fight with an ideological group such as Azov Battalion.”
Questions have arisen over the legality of British citizens going abroad to fight in previous foreign conflicts.
In 2014, prosecutors gave a warning that UK citizens who went to fight in the Syrian civil war could be committing an offence, even if they joined the rebels fighting to overthrow President Bashar Al Assad.
The UK has previously, and unsuccessfully, attempted to prosecute its citizens who had travelled abroad to fight terrorist forces.
The country brought terrorism charges against individuals who had joined Kurdish military unit, the Yekineyen Parastina Gel (YPG), in their fight against ISIS.
None of the cases relating to the YPG led to a guilty verdict and most prosecutions were discontinued before a jury was asked to adjudicate.
Mr Hall has previously questioned the use of terrorism charges against the individuals who fought for the YPG, in his annual terrorism report.
"Given this wide definition of terrorism and lack of applicable defences, the YPG cases must be seen as examples of the importance of the prosecutorial discretion in terrorism cases," he said.
Despite Ms Truss's support of UK citizens wishing to fight, Defence Secretary Ben Wallace has spoken of how the “very dangerous” situation could lead to them being killed.
Mr Wallace, who has served in the armed forces, criticised the foreign secretary's comments and said he did not “want to see British people killed any more than I want to see Ukrainians” dying. There were "better ways" to support Ukraine, he said.
“If you’re keen to help and you’re a UK citizen, come and join our armed forces," he told Sky News.
“Look, there are people who will go … I think what I would say is unless you are properly trained, unless you are an experienced member of an armed forces, I think there are better ways for you to contribute to the security of Ukraine.”
Armed Forces Minister James Heappey said he "probably wouldn't" agree with Ms Truss's remarks.
“The travel advice is that UK nationals should not travel to Ukraine," he said.
“But if people are filled with a desire to stand up for freedom, like generations of young people before them, they would be very, very welcome at their nearest army, navy or air force recruiting office."