Ukraine used British Tanks during its surprise incursion into Russia, it has been reported.
Military sources told Sky News that Challenger 2 tanks took part in the daring advance, which left Vladimir Putin stunned.
Kyiv’s troops launched a cross-border attack on the southwestern Kursk region, 330 miles from Moscow.
The Russian president described it as a “major provocation” and accused Ukraine of the “indiscriminate shelling of civilian” targets.
The Ukrainian operation came two-and-a-half years after Russia invaded its neighbour, sparking the ongoing conflict.
Britain is among a number of western countries supplying Ukraine with military hardware to defend itself.
The Ministry of Defence said it could not comment on “operational” matters, but confirmed there had been no change of policy since the government said Kyiv was free to use UK weapons on Russian soil.
The Ukraine army’s 82nd Air Assault Brigade, which has been using British tanks, took part in the incursion, which was launched last week.
Ukraine now claims to control 386 square miles (1,000 square km) of the Kursk region, according to Associated Press news agency.
Reports from Moscow say more than 8,000 Russians have been evacuated, and more than 6,000 put into temporary accommodation centres.
Earlier this week, Vladimir Putin said Ukraine was waging war against Russia “with the help of its western masters”.
“The enemy will continue to try to destabilise the situation in the border zone, in order to shake up the internal political situation in our country,” the president said, according to Reuters.
Ukraine’s president Volodymyr Zelenkyy said: “It is only fair to destroy Russian terrorists where they are, where they launch their strikes from. Russian military airfields, Russian logistics.
“We see how useful this can be for bringing peace closer. Russia must be forced into peace if Putin wants to continue waging war so badly.
“Russia brought war to others, and now it is coming home.”