A Russian fighter jet fired a missile near a British RAF spy plane in a “dangerous” escalation over the Black Sea.

The unarmed RAF Rivet Joint RC-135W ‘nuke sniffer’ plane was on a routine patrol over the Black Sea, south of Crimea, on September 29 when it was tailed by two Russian Su-27 fighter jets.

They followed the British plane for 90 minutes before one of them opened fire, UK Defence Secretary Ben Wallace told the House of Commons on Thursday.

The shocking escalation shows just how dangerously the world is teetering on the edge of a third world war.

“On September 29 an unarmed RAF RC-135 Rivet Joint, a civilian-style aircraft on routine patrol over the Black Sea was interacted with by two Russian armed SU-27 fighter aircraft,” Wallace said.

“It is not unusual for aircraft to be shadowed and this day was no different.

“During that interaction however, it transpired that one of the SU-27 aircraft released a missile in the vicinity of the RAF Rivet Joint beyond visual range.

Britain's Defence Secretary Ben Wallace, front, arriving at Downing Street in London. Photo / Frank Augstein, AP, File

“The total time of the interaction between the Russian aircraft and the Rivet Joint was approximately 90 minutes.

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“The patrol completed and the aircraft returned to base.”

Wallace said the firing of the missile was a “technical malfunction” and that it was not considered to be deliberate.

The UK Rivet Joint is known as a ‘nuke sniffer’ as it tests the atmosphere for radioactivity and it can also read enemy communications from a long distance away.

Wallace said he had spoken to Russian defence minister Sergei Shoigu and Moscow’s chief of defence staff.

“In my letter I made clear the aircraft was unarmed, in international airspace, and following a pre-notified flight path,” Wallace said.

“I felt it was prudent to suspend these patrols until a response was received by the Russian state.

“The reply by the Russian minister of defence on October 10 stated they have conducted an investigation into the circumstances of the incident and stated it was a technical malfunction of the SU-27 fighter.

“They also acknowledge that the incident took place in international airspace.”