British counterterrorism police held two men on Monday following a "security threat" aboard a Ryanair flight that led to fighter jets being scrambled to intercept it.

Police said they detained the pair, a 34-year-old man from Kuwait and a 48-year-old man from Italy, under terrorism laws late on Sunday at Stansted Airport after the flight from Vienna landed.

Britain's Royal Air Force (RAF) said it had launched two Typhoon fighter jets from a base in nearby Lincolnshire "to intercept a civilian aircraft". 

"The aircraft was escorted safely to Stansted," it added.

A spokesman for budget carrier Ryanair said the plane's crew had been alerted to a "potential security threat on board".

"In line with procedures, the captain informed UK authorities and continued to London Stansted, where the aircraft landed normally and taxied to a remote stand where passengers disembarked safely," said the airline.

"Passengers in London Stansted waiting to depart to Vienna were transferred to a spare aircraft to minimise the delay to their flight."

Police said inquiries were ongoing.