Canada and the United States are closely watching the diplomatic row after Britain dismissed a Russian warning over the Ukraine war.
Russian embassy warning
Britain flatly dismissed a threat by Russia over the Ukraine war, saying: "We won't be bullied."
In a statement through its Embassy in London, Russia threatened the United Kingdom with "consequences" after reports that British drones have been used to strike targets on Russia's mainland for the first time.
Ukraine used drones made by two UK companies as part of a so‑called deep strike campaign, the Sunday Times reported.
Both Canada and the United States have pledged continued military aid to Kyiv and say they will watch any escalation closely. The two neighbours often coordinate their diplomatic responses with London on matters of European security.
British government response
The Russian Embassy to the UK said in a statement on Monday that the reports "confirm that London is deliberately opting for an escalation of the Ukraine crisis" and accused Britain of "seeking to contain Russia and inflict maximum damage on it by proxy".
"London's actions will inevitably carry consequences for which it will have to answer," it added.
"The deeper its involvement in the conflict and the greater its support for Kyiv's terrorist machinery, the higher the price it will pay."
Work and pensions minister Lilian Greenwood, on the media round for the Government, said: "Well, our message back to the Russians is that we stand with Ukraine. We've stood with Ukraine throughout this time…the Russian illegal invasion. We will continue to do so, and we won't be bullied in this way."
New Prime Minister Andy Burnham has already hosted Ukraine's president Volodymyr Zelensky at No 10 to show Britain's ongoing support for Kyiv against Vladimir Putin's war.
A Ministry of Defence spokesperson said: "Britain stands shoulder to shoulder with Ukraine and we are committed to providing the equipment Ukraine needs to defend itself against Putin's illegal invasion. Russia should be in no doubt about the resolve of this Government to stand against Russian aggression, in Ukraine and against the UK and our allies."
Ukraine's strategy of long‑range drone strikes is believed to be aimed at cutting Moscow's revenue for the war and making Russian citizens feel the impact of the invasion.
It launched three times as many of those strikes in July as it did in January, according to data from Acled, an independent conflict monitor.
Repeatedly hitting deep into Russia has forced its military to stretch air defences over a larger area.
Russia's Ministry of Defence said on Saturday that it had shot down 598 Ukrainian drones over 19 Russian regions, as well as the Black and Azov Seas and the annexed Ukrainian peninsula of Crimea.
Officials on Monday said Ukrainian long‑range attacks on Russia killed seven people overnight, while five civilians died in Ukraine after strikes by Moscow's forces.