"UK special forces have been deployed to the region to help and advise the Ukrainian military. They have a wide skill set which will no doubt be very useful to the Ukrainian forces", the source said as quoted by the Mirror.
The British troops from the SAS, the SBS, the Special Reconnaissance Regiment and the Special Forces Support, which are no longer engaged in Afghanistan, are expected to teach Ukrainian special forces counter-insurgency tactics, sniping and sabotage, according to the source.
The precarious situation around Ukraine has deteriorated in recent weeks with the United States and European Union voicing concerns over the Russian military buildup at the Ukrainian border, and NATO urging allies to enhance their military support for Kiev.
US soldiers are pictured prior the beginning of the official welcoming ceremony of NATO troops in Orzysz, Poland, on April 13, 2017.
© AFP 2023 / Wojtek RADWANSKI
So far, the US, UK, Canada, Poland and Baltic states have supplied several batches of weapons to Ukraine, with Washington dispatching additional forces to neighbouring Poland and Romania.
Russia in turn has repeatedly denied having intentions to invade any country, pointing to NATO's military activity near its borders, which it deems a threat to its national security.