Quick reaction RAF typhoon fighters have been launched to an exercise south of Sumburgh.
The RAF Voyager tanker, used for air-to-air refuelling, has also flown from RAF Brize Norton in Oxfordshire to the scene.
RAF spokesman Martin Tinworth said they “do not offer comment on ongoing operations”.
He did not confirm whether this was a training exercise, or a different incident.
The RAF posted on Twitter on Saturday that typhoon aircraft were scrambled to intercept two Russian aircraft off the coast of Scotland.