Predictably, the Kremlin is fuming at widespread reports that the Biden administration has made a U-turn on its policy which previously prohibited Ukraine from attack Russian soil with US-supplied weaponry.

Former Russian president and current Security Council Deputy Chairman Dmitry Medvedev has warned that Russian forces could strike back from any point where attacks are launched, including on "NATO specialists" advising Ukraine forces.

"NATO countries that have approved strikes with their weapons on Russian territory should be aware that their equipment and specialists will be destroyed not only in Ukraine, but also at any point from where Russian territory is attacked," he said on Telegram, according to TASS, also noting that "the participation of NATO specialists could be seen as a casus belli."

"All their military equipment and specialists fighting against us will be destroyed both on the territory of former Ukraine and on the territory of other countries, should strikes be carried out from there against Russian territory," Medvedev added in the warning.