Sentinel R1 aircraft have flown three missions skirting the Russian exclave of Kaliningrad

RAF spy planes have been monitoring the deployment of nuclear-capable ballistic missiles in Kaliningrad.

Three missions by Sentinel R1 aircraft skirting the borders of the Russian exclave have been mounted this year. The jets, flown from RAF Waddington in Lincolnshire, carry radar that can pinpoint the location of military units on the ground.

Defence sources say they have been tasked with spying on Iskander missiles deployed to Chernyakhovsk military base and protected by long-range air defence and coastal defence missiles.

Greg Bagwell, a retired air marshal and former deputy commander for RAF operations, described the deployment of Iskanders as a “provocation”. “When someone brings out new kit you always want to go and have a look at it,” he added.