The head of the United Kingdom's armed forces Admiral Tony Radakin said, on Sunday, that sending Britons to fight against Russia in Ukraine is "illegal and unhelpful."

"We've been very clear that it's unlawful as well as unhelpful for UK military and for the UK population, to start going towards Ukraine," Chief of the Defence Staff Radakin told BBC television.

"Support from the UK, support in whatever way you can. But this isn't really something that you want to rush to, in terms of the sound of gunfire."

"I think she was reflecting... that we can all understand that sentiment, and that sentiment needs to be channeled into support for Ukraine, but we're saying, as professional military people, that actually that is not necessarily the sensible thing to be doing," Radakin added.

Last week, British Foreign Secretary Liz Truss said that she backs anyone who wanted to volunteer and follow an appeal for foreign fighters to come to Ukraine from Ukrainian President Volodymyr Zelensky.

Truss added that she would "absolutely" support Britons wanting to go to Ukraine to fight, and an unknown number have already gone.

Zelensky has urged foreigners to visit Ukrainian embassies around the world to join an "international brigade" of volunteers fighting Russian forces.

Britons have traveled to Ukraine to join the Ukrainian aggression against Donbass area since 2014.

Fighters from Europe, the US, and Australia have joined up too.

Ukrainian army’s aggression against Donbass area has led to more than 10,000 deaths and displaced more than 1.6 million people, says the UN.

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