NATO has reported an "unusual" spike in Russian military flights over the Black, Baltic and North seas and the Atlantic Ocean over the past two days.

Alliance military spokesman Lieutenant Colonel Jay Janzen said on Wednesday that four groups made up of Tu-95 Bear H strategic bombers, MiG-31 fighters and other Russian warplanes had been conducting large-scale manoeuvres in international airspace.

He said Norwegian, British, Portuguese, German, Danish and Turkish fighters were scrambled in response, as well as planes from the non-NATO nations of Finland and Sweden.

No incidents were reported, but Janzen said the manoeuvres were unusual in their size.

Tensions have been running high between NATO and Russia since Russia annexed the Crimean Peninsula from Ukraine in March.

According to NATO officials, alliance pilots have conducted over 100 intercepts of Russian aircraft this year, or about three times more than in 2013.

Source: Associated Press