OTTAWA - A Canadian frigate taking part in a NATO exercise in the Black Sea was buzzed by Russian military jets off the southern coast of Ukraine on Sunday.

Defence Minister Rob Nicholson calls the incident unnecessarily provocative and says it risks escalating tensions in the region even further at a time when a fragile ceasefire is just taking hold.

The minister says the planes circled HMCS Toronto in a manner that did not pose a threat.

Reports say three aircraft, two fighters and a surveillance plane, were involved.

The U.S. Navy is leading the three-day exercise in conjunction with Ukraine, the 13th time the exercise has been held since the former East Bloc country began making overtures to join NATO.

The drill was planned long before relations with Russia soured over Moscow's annexation of Crimea and intervention in eastern Ukraine.