Defence Secretary Michael Fallon has insisted that Nato would stand by its eastern European members as RAF jets based in Estonia were scrambled to intercept Russian aircraft on three separate occasions in 24 hours as he visited the region.
The Typhoon fighters, based at Amari as part of Nato's Baltic Air Policing mission, escorted and identified the Russian planes which had approached Estonian airspace.
Mr Fallon visited the airbase as part of a tour of eastern Europe as tensions continued over Russia's role in the Ukraine crisis.
The incidents involved Russian Mig 31 Foxhound fighters, a TU22 Backfire bomber, an AN6 Curl transport plane and an A50 Mainstay airborne warning and control aircraft.
A spokesman said: "The RAF can confirm that RAF Typhoon fighters based at Amari in Estonia have launched to intercept unidentified Russian aircraft approaching the Baltic nation's airspace three times in the last 24 hours.
"A variety of Russian aircraft were intercepted, escorted and identified, including Mig 31 Foxhounds, a TU 22 Backfire, a AN 26 Curl and a Mainstay A50."
Four RAF Typhoons and their support crews are deployed in Estonia until August in support of the Nato mission.
Mr Fallon, who met pilots and ground crew involved in the mission, said: "I am hugely proud to see the men and women of the RAF continuing their watch over our allies on the eastern borders of the Nato alliance. Our on-going presence here sends a clear message that we will stand with our eastern European partners.
"The UK has a pivotal role to play in ensuring global security, and if we fail to defend our allies as well as ourselves, we risk encouraging adventurism and instability elsewhere in the world."
Typhoon pilot Flight Lieutenant Oli Fleming, who flew on the first scramble, said: "It's not unusual for Russian aircraft to appear in the vicinity of our military assets during large exercises. Nevertheless, we remain ready, willing and able to intercept and defend the Baltic nations airspace as we have demonstrated today."
The Defence Secretary had earlier visited the Royal Navy's flagship HMS Ocean which was taking part in the US-led, Nato-linked Baltops exercise in Poland.
The UK has also deployed the frigate HMS Iron Duke and minehunter HMS Quorn to take part in exercises.
Meanwhile more than 200 soldiers from The Royal Gurkha Rifles are conducting land warfare exercises with Nato allies across the Baltic States and Poland, as part of Exercise Saber Strike.
Mr Fallon said: "The participation of nearly 1,000 UK personnel and the Royal Navy's Flagship HMS Ocean in these exercises sends the strongest possible message about our determination to defend and support our allies in the face of any threat.
"This exercise is a demonstration of what the Royal Navy does best, and why our armed forces are among the most respected in the world; our ability to combat any threat to the security of the UK, to defend and strengthen our partners and to project UK capabilities anywhere in the world."