The US bombers were in the Baltic Sea region to train together with their Nato ally Finland, which shares a 1,340km border with Russia, amid escalating tensions stemming from Western backing for Ukraine to counter Russia’s invasion.

Monday’s interception of the US bombers by Russian fighter jets came just days after Russia fired a hypersonic intermediate-range ballistic missile at Ukraine last Thursday in response to a decision by the US and Britain to allow Kyiv to strike Russian territory with advanced Western weapons.

The US bombers did not change their pre-planned flight pattern during what was deemed a safe and professional intercept by the Russian SU-27s, the US official told Reuters.

On Monday, the US B-52s also flew with Finnish F/A-18Cs during a US-Finnish drill in Finnish airspace.

The Finnish Air Force said in an emailed statement to Reuters that its fighter jets and the US bombers had flown a training mission in Finnish airspace on Monday as part of efforts to strengthen Finland’s defence capability.

The Finnish air force statement did not address the Russian intercept but said the drill had included “simulated air-to-ground drops [to] demonstrate our ability to work together in fire-use missions”, adding the cooperation also contributed to Nato’s collective defence and deterrence in the far north.

In an abrupt departure from its long-standing policy not to align itself militarily, Finland joined Nato in 2023 in direct response to Russia’s full-scale invasion of Ukraine in 2022.

Having fought back an invasion attempt by the Soviet Union during World War II, Finland has been among the staunchest European supporters of Ukraine in its attempt to push back the Russian invaders.