Moscow (AFP) - The Russian defence ministry said on Tuesday that its planes had not approached a Canadian frigate on a NATO mission in the Black Sea in an incident Ottawa denounced as "unnecessarily provocative".

Moscow said an Sukhoi Su-24 attack aircraft and an Antonov An-26 transport plane were carrying out "planned flights over neutral waters of the Black Sea near the Russian Federation's state border".

"The flightpath of the planes of the Russian airforce ran through an area where the HMCS Toronto was located, without approaching the foreign military vessel," Major General Konashenkov told Russian news agencies.

Canadian Defense Minister Rob Nicholson said on Monday that a Russian military plane had circled over the HMCS Toronto, a Canadian frigate in the Black Sea, where NATO and Ukraine are holding naval exercises.

The Russian aircraft "did not in any way pose a threat to the Canadian ship", Nicholson said but added that "their actions were unnecessarily provocative and risk escalating tensions even further" in the region.

The HMCS Toronto left Canada's Atlantic coast at the end of July with 250 sailors and Sea King helicopters on board to join the NATO mission.

Russia and the West are locked in a dramatic standoff over a crisis in Ukraine where Kremlin-backed separatists are battling against pro-Western Kiev authorities.

Ukraine said on Monday it had launched three-day naval exercises with US-led NATO forces in the Black Sea aimed at guaranteeing its security.