Russian military aircraft are still committed to provocations over the Black Sea, Bulgaria's Defense Minister Angel Naydenov has warned.

In an interview for the newspaper 24 Chasa, Naydenov has asserted that no violation of Bulgarian airspace could be observed. He has hinted, however, that the purpose of their flights is more than clear to his Ministry.

"You don't think that [Russian aircraft] are flying just for an innocent air stroll or to flap their wings at sea tourists, do you?" Naydenov asked.

He made clear that the Ministry of Defense was closely monitoring the situation and could turn to NATO for help anytime it perceives a risk.

Depending on the level of threat, NATO orders are issued "every day" to send a plane up into the airspace, Naydenov added, when asked why Bulgaria's fighter jets are made to fly in response to Russia's military presence over the Black Sea.

Last week Bulgaria's President Rosen Plevneliev warned that Russian military aircraft making flights over the Black Sea, near Bulgarian air space.

He said that Russian maneuvers are virtually exhausting Bulgarian fighter jets, which in response have been recently raised with a frequency that is unprecedented over the last 20 years.

Russia's Ambassador to Bulgaria Yuriy Isakov later refuted claims his country's army was committed to any type of air provocations, pointing out instead that US naval presence in the Black Sea was more of a concern.

US and French vessels are now in the Black Sea, after Pentagon officials announced earlier they were sending USS Donald Cook to show support of Ukraine's side in its standoff with Russia and to prevent tensions from escalating in the region.