A group of around 30 elite British troops has arrived in Ukraine to help train the Ukrainian armed forces on new anti-tank weapons gifted by the UK amid fears of an imminent, new Russian invasion, Sky News understands.

The members of the Ranger Regiment - part of the army's newly-formed Special Operations Brigade - flew out on military planes that also airlifted a total of some 2,000 anti-tank missile launchers to the country during the course of this week.

British surveillance aircraft have also been spotted as part of a quiet but notable build-up of support to Ukraine's military by the UK.

Sky News understands that "several" flights have taken place since Monday.