Two British Typhoon jets based in Romania have scrambled to investigate suspected Russian fighter aircraft operating near NATO airspace over the Black Sea.
Britain's Ministry of Defense said the Typhoons launched from the Mihail Kogalniceanu Air Base near the Romanian city of Constanta on August 21 when two suspected Russian Su-30 Flanker aircraft appeared to be heading toward NATO airspace from the Crimea region.
There was no immediate comment from Russian officials.
Encounters between Russian and NATO warplanes have increased in recent years as Moscow demonstrates its resurgent military might.
Russia has also increased its navy's presence in the Mediterranean, Black Sea, and other areas.
Tensions are high in the region since Moscow's 2014 takeover and illegal annexation of Ukraine's Crimean Peninsula, a move that led to Western sanctions being imposed against Russia.
The British Typhoons were operating in accordance with NATO’s enhanced air policing mission designed to deter "Russian aggression, reassure Romania and assure NATO allies of the UK commitment to collective defense," the Defense Ministry said in a statement.
It quoted one of the Typhoon pilots as saying, "We had radar contact and shadowed the two aircraft as they flew through the Romanian flight information region, but we never got within visual range to see them."
Airspace is divided into flight information regions, in which flight and alerting services are provided by a specific country's aviation authority and differs from sovereign airspace.
The statement did not specify if the Russian jets flew into actual Romanian airspace.