New defence secretary Wes Streeting has criticised a live-fire military exercise carried out by a Russian warship around 40 nautical miles (46 miles) off the British coast, calling it "performative and irresponsible".
The vessel, which was shadowed by a Royal Navy ship, carried out the artillery manoeuvre south of Plymouth on Monday.
Moscow's warship, The Neustrashimy, has been escorting Russian 'shadow fleet' oil tankers through the English Channel.
A Ministry of Defence spokesperson said: "A Russian naval vessel shadowed by the Royal Navy conducted a live-fire weapons exercise in international waters approximately 40 nautical miles south of Plymouth yesterday.
"The Royal Navy monitored that exercise throughout, continues to track the vessel's activity closely, and stands ready to protect UK national security."
Mr Streeting told reporters on Monday: "We should see yesterday's events as performative and irresponsible.
"It's not the first time that Russia has behaved like this, and frankly, it's the tip of the iceberg of the daily threats that this country faces and our allies face."
He added: "Russia should be in no doubt about the resolve of this government and this prime minister."
Before the exercise, the Russian vessel informed HMS Tyne of its intention to conduct gunnery activity.
It then requested that HMS Tyne reposition to a safer distance, which it did.
The exercise was carried out in international waters and lasted for 30 minutes.
Dmitry Peskov, Vladimir Putin's spokesman, said: "All exercises and actions of our warships are carried out in strict accordance with international maritime law.
"Therefore, there is no need to see any hints here. But, in turn, of course, the arrival of the new UK Prime Minister, probably one of his first actions was the remark of unconditional support for Ukraine, therefore, about Britain's intention to keep doing everything for the war to continue. This is a fact, which we, of course, are noting."
This latest incident is the second Russian warship to escort a so-called shadow tanker through the Channel in recent weeks.
Sky News' helicopter tracked The Neustrashimy as it was refuelled in the North Sea by a Russian navy ship earlier this month.
Last month, its predecessor, Admiral Grigorovich, fired warning shots at a British couple sailing a yacht.
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That same month, the captain of another Russian shadow fleet tanker was detained by the UK and charged with contravening sanctions.
Royal Marine commandos and NCA officers landed from a Chinook helicopter and seized the tanker in the Channel 25 miles south of the Isle of Wight.
Earlier in June, the French navy aided by British forces, intercepted another oil tanker under international sanctions that was coming from Russia.
In March, the UK helped the French navy seize another vessel, a Mozambique-flagged ship called the Deyna, in the Mediterranean.
It was sanctioned by the UK and the European Union for its role in shipping Russian oil.
The same month then-PM Sit Keir Starmer allowed British forces to seize shadow fleet vessels, leading the ships to veer way from the English Channel.
(c) Sky News 2026: New defence secretary Wes Streeting hits out at Russia after live-fire exercise 40 miles off UK coast
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