Bulgarian Defense Minister Nikolay Nenchev Bulgaria Ministry of Defense

MOSCOW (Reuters) - Russia on Monday rejected allegations by Bulgaria that its aircraft had been involved in violations of Bulgarian airspace, Russian news agencies reported.

On Sunday, Bulgarian Defence Minister Nikolay Nenchev said there had been a rise in violations of its airspace by Russian military and commercial aircraft in the past month, calling the alleged breaches "provocations".

A spokesman for Russia's Defence Ministry said Russian aircraft flying over the Black Sea had followed international rules and confined themselves to neutral zones, the Interfax news agency reported.

He said Russian aircraft had kept their transponders on at all times, and that the ministry had not received any protests from Bulgaria, contradicting allegations by Bulgaria.

Nenchev had told Bulgarian television channel Nova TV the planes had turned off their transponders – communications devices that, alongside normal radars, make it easier for an airplane to be located, especially in congested airspace.

(Reporting by Jason Bush; Editing by Alison Williams)