Thousands more elite Russian special forces are flooding into Belarus escalating fears of an imminent Ukraine invasion.
The 14th Spetsnaz Brigade of 2,000 crack assassins, sabotage experts and covert operatives are on their way to Ukraine’s northern neighbour.
They will bolster at least 5,000 Spetsnaz already there who are among 80,000 regular soldiers from Russia and Belarus.
News of more of Russia’s SAS-style troops entering Belarus has heightened alarm over the Kremlin’s military build-up against Ukraine.
At least 126,000 Russian forces are already gathered on Ukraine’s eastern flank and off the coast in navy warships.
Russia has claimed the Belarus build-up is for joint exercises with local forces, although the numbers are way over the threshold for non-lethal wargaming.
On Tuesday a UK security source told the Daily Mirror: “So many Spetsnaz in the region is a very worrying development.
“In times of war the primary function of Spetznaz troops is infiltration, insertion behind enemy lines, either in uniform or civilian clothing.
“This is usually well before hostilities begin and once in place to commit acts of sabotage, destruction of communications, logistics centres and the assasination of key government leaders and military officers.”
Ukrainian President Volodymyr Zelenskiy has boosted his armed forces by 100,000 troops over three years and raised soldiers’ pay.
More than 1,000 civilians in Kyiv are being trained up as citizen warriors to help defend against a Russian invasion.
There are currently nearly 250,000 people in Ukraine’s armed forces, compared to Russia’s overall strength of around 900,000.
Many Ukraine troops are manning a 250 trench frontline facing pro-Russian separatists in contested Donbas where 14,000 have died in bitter fighting since 2014.
NATO has rallied round Ukraine in recent weeks with Britain arming and training Ukraine troops with NLAW anti-tank missiles.
Ahead of a visit to Kyiv Prime Minister Boris Johnson said: “We urge Russia to step back and engage in dialogue to find a diplomatic resolution and avoid further bloodshed.
“As a friend and a democratic partner, the UK will continue to uphold Ukraine’s sovereignty in the face of those who seek to destroy it.”
Thousands of British people who live in Ukraine are preparing to evacuate via Kyiv, possibly fleeing west of the capital or fly back to the UK if the airports are not blitzed.
NATO spy planes are monitoring Russia’s troop build-up in Belarus to search for early warning signs of an invasion into neighbouring Ukraine.
An American air force Rivet Joint RC-135 reconnaissance plane scanned the Belarus border on Tuesday before swooping towards Crimea.
The warplane was flying at over 31,000 feet at 314 knots to stay out of range of ground-to-air missiles from the Belarus side.
Both areas are believed to be possible staging points for a Russian attack on Ukraine if the Kremlin orders an invasion.
British Rivet Joint spy planes are also believed to be involved in scanning Belarus and Crimea for possible invasion signs.
The £200 million warplane is filled with high-tech equipment capable of hoovering up communications on the ground.
It can also detect signs of missile systems being lined up for an attack and geolocate where they are by tracking their guidance systems.