UK fighter jets intercepted a Russian maritime patrol aircraft after it “repeatedly approached” a carrier strike group in the Norwegian Sea, the Ministry of Defence (MoD) said.

The Russian Bear-F plane passed at low altitude and “unnecessarily close” to the HMS Prince of Wales aircraft carrier and is believed to have dropped 10 sonobuoys into the water on Thursday, the MoD added.

The MoD said Moscow’s activity in the Norwegian Sea was “unsafe and unprofessional”.

It comes weeks after Royal Marines boarded a Russian shadow fleet oil tanker in the English Channel, while the head of the military has warned the risks and threats facing the UK are greater now than at any time since the Cold War.

The UK’s Carrier Strike Group is currently deployed off Iceland under Nato command, with 1,500 British personnel on board.

The group consists of HMS Prince of Wales, Type 45 destroyer HMS Duncan, F-35 jets, Merlin and Wildcat helicopters, and is supported by RFA Tidespring, a replenishment tanker.

It is the first time Nato has conducted air policing operations from a European aircraft carrier.

The monitoring devices which were believed to have been dropped by the Bear-F plane float on the water and use sonar to detect submarines and other vessels.

British forces attempted to contact the Russian plane on international frequencies, but it did not respond.

Two F-35 jets then flew from the Prince of Wales to escort the Bear-F away from the Carrier Strike Group.

Defence Secretary Dan Jarvis visited British forces on board the flagship HMS Prince of Wales over the weekend.

“We live in an increasingly dangerous and uncertain time, and it’s deployments like this, supported by allies and partners including Iceland, that improve our deterrence and defence as part of Nato,” he said.

He told Channel 4 News: “We should be clear-eyed about the fact that the threat from Russia exists in every domain, under the water, on the water, on the land, in the sky, in space and in cyberspace as well.”

Chief of the Defence Staff Sir Richard Knighton told the BBC in June that Russia had been “probing, challenging, testing our defences”, and was “raising the stakes and risks crossing a line”.

Nato has warned that Russia could be ready to use military force by 2030.

The government published the UK’s long-delayed plan to invest in defence last week, with outgoing Prime Minister Sir Keir Starmer setting out a £15bn increase in military spending, part of which will be funded by cutting budgets in other government departments.

Opposition MPs and military figures have criticised the level of investment, saying it does not go far enough to meet the scale of the threat posed by Russia.

John Healey and Al Carns resigned from Sir Keir’s government in June over a previous version of the plan, contributing to the prime minister’s downfall.