Britain said on Sunday two of its fighter jets had intercepted Russian aircraft over the Baltic Sea close to NATO alliance airspace in separate incidents on Tuesday and Thursday.

The Typhoon fighters were scrambled to intercept a Russian Ilyushin Il-20M "Coot-A" intelligence aircraft on Tuesday, Britain's Ministry of Defence said in a statement.

Two day later, two Typhoons intercepted an unknown aircraft leaving Kaliningrad air space, it said.

Minister for the Armed Forces Luke Pollard said with Russian aggression growing and security threats on the rise, Britain was stepping up to reassure its allies, deter adversaries and protect its national security.

"This mission shows our ability to operate side by side with NATO's newest member Sweden and to defend the Alliance's airspace wherever and whenever needed, keeping us safe at home and strong abroad," he said in a statement.

There was no immediate reaction from Russia.