Royal Air Force fighters have intercepted Russian jets approaching Estonia for the second time in a week, the Ministry of Defence said.
The Typhoons were scrambled to meet five unidentified aircraft in international airspace near the Baltic State's borders on Tuesday.
They shadowed two Su-27 Flanker fighters and an IL-20 "Coot-A" reconnaissance aircraft north of Estonia before two more Su-27s were detected and met, the MoD said.
A spokesman said the Russian aircraft "were operating without transmitting recognised identification codes nor were they communicating with regional air traffic control centres".
It comes after an incident on Friday when Typhoons from Amari air base in Estonia intercepted three Russian transport aircraft approaching the Baltic in similar circumstances.
Four RAF jets were last month deployed to join the Baltic Air Policing mission - which sees Nato members help others who do not have their own policing capabilities - and will remain there until the end of August.