A spokeswoman for the Ministry of Defence said there were "unidentified aircraft flying near the north of Scotland".
The RAF are understood to have identified them as Russian aircraft.
"They were flying in international airspace at all times, they didn't go into UK sovereign airspace," she added, saying there had been eight similar incidents in 2013.
It was reported that there were two Russian planes, believed to be Tupolev-95s, which had turned away and flown towards Scandinavia after being contacted by the British jets.
Defence experts says Russia uses such surveillance flights to remind the world of its military might and to probe other countries' air defence systems.