A Russian fighter jet was dispatched to intercept a US B-52 strategic bomber after its appearance in neutral airspace over the Baltic Sea irked Moscow, according to the Russian defence ministry.

A Russian Sukhoi-27 of the Russian Baltic Fleet was "dispatched to intercept the target" and "approached the aircraft staying at a safe distance, identified it as a US strategic bomber B-52 and escorted it for some time", the Russian media quoted the ministry as saying.

It added that the nuclear-capable American bomber was flying along Russia's border. The incident that took place on Tuesday (6 June) at 7am GMT is reported to have had echoes of the Cold War, Reuters noted.

A former Russian Air Force commander called the move by the B-52, a long-range bomber that first went into service in the 1950s, "disrespectful".

A Pentagon spokesperson, Captain Jeff Davis, said the US bomber was on a "routine mission" over the Baltic Sea. However, the crew had not been debriefed about the intercept, which means the Pentagon is yet to ascertain exactly how close the Russian Su-27 flew near the US bomber, according to Fox News.

But Davis claimed that the "vast majority" of Russian intercepts are safe and professional.

The US bomber along with 800 airmen was deployed to the UK Royal Air Force base Fairford in England from the Barksdale Air Force Base in Louisiana earlier this month for training exercises with Nato allies as a show of strength against Russia. The military exercises are set to take place in the Baltic Sea, the Arctic and in several Nato member- states which share a border with Russia.

Russian Foreign Ministry official Mikhail Ulyanov warned that the US' flight near Russian borders would not help ease tensions between the West and Moscow.

"The fact that Nato forces are converging near Russia's borders and carrying out military exercises supported by strategic bombers from the USA capable of carrying nuclear weapons hardly helps de-escalate tensions in Europe," Sputnik quoted Ulyanov as saying.

North Korea US B-52 bomber
B-52 Stratofortress bombers are deployed to the UK Royal Air Force base Fairford for training exercises with the Nato allies Tim Chong/Reuters

The US B-52 Stratofortress bombers are reported to be capable of carrying nearly 31,000kg payload for more than 8,000 miles.

Nato said as many as 4,600 of its troops will participate in the exercises, which are seen as a move to counter Russia's alleged aggressive military position in the region.

In a separate incident, Russia said its MiG-31 fighter jet had intercepted a Norwegian patrol plane – identified as a P-3 Orion anti-submarine aircraft - over the Barents Sea later on Tuesday. The Norwegian plane reportedly had its transponders switched off, Moscow complained.

The Norwegian military confirmed the encounter but called it a "normal" intercept. It said there was nothing illegal or unusual about its military plane not using a transponder.

However, Russia is reported to have been irked more by the US B-52 bomber's appearance near its airspace.

Pyotr Deinekin, a former Russian Air Force commander, said he could not remember when was the last time a US B-52 bomber flew over the Baltic Sea. So the latest flight raises troubling questions, he said.

"Such behaviour does not deserve respect," Interfax news agency cited Deinekin as saying.

Sukhoi 27 fighter jet
A Russian Sukhoi Su-27 fighter jet intercepted a US plane over the Baltic Sea ~ file photo Wikipedia

He noted that the B-52 was designed in the 1950s to attack Russia's crucial targets via the North Pole in the event of a nuclear war when the Soviet Union still existed.

"Strategic bombers should not fly so close to our land borders," he said as he called on Russia to ascertain what weapons the B-52 was carrying.