NATO announced it has detected “unusual” activity by Russian aircraft in European airspace in the past two days.
The alliance said that more than two dozen Russian aircraft in four groups were intercepted and tracked on Tuesday and Wednesday.
According to NATO, the Russian forces have been "conducting significant military maneuvers" over the Baltic Sea, the North Sea and the Black Sea.
A NATO spokesman said the Russian warplanes have included Tu-95 strategic bombers and MiG-31 jets, and added that Norwegian, British, Portuguese, German and Turkish fighter jets have been scrambled to intercept and identify the Russian aircraft.
Tensions between NATO and Russia have escalated since Russia annexed the Crimean Peninsula from Ukraine in March, and there have been more than 100 intercepts of Russian aircraft in 2014 alone, three times more than in 2013.
NATO's eastern members, including Poland and the Baltic states, have been particularly annoyed by Russian military activity. In response to their concerns, the U.S.-led alliance has increased the number of aircraft and personnel to monitor the airspace on a rotational basis.
Meanwhile, Russia said Wednesday that the controversial handover of a French warship would take place on November 14, but the manufacturer immediately denied the deal had been settled.
France has previously said conditions were "not right" for the deal, and President Barack Obama has said it would have been “preferable to press the pause button” over it.
EU leaders have warned that Russia will use the warship to threaten its neighbors.
Named Vladivostok, the warship is the first of two Mistral-class amphibious assault ships Russia ordered from France in a contract worth $1.6 billion.