Russia on Monday threatened to strike British military facilities and said it would hold drills simulating the use of battlefield nuclear weapons amid sharply rising tensions over comments by senior Western officials about possibly deeper involvement in the war in Ukraine.

After summoning the British ambassador to the Foreign Ministry, Moscow warned that Ukrainian strikes on Russian territory with U.K.-supplied weapons could bring retaliatory strikes against British military facilities and equipment on Ukrainian soil or elsewhere.

The remarks came on the eve of Russian President Vladimir Putin’s inauguration to a fifth term in office and in a week when Moscow on Thursday will celebrate Victory Day, its most important secular holiday, marking its defeat of Nazi Germany in World War II.