Bulgaria probably used to pay twice the normal price for the maintenance contracts it had with Russian company RSK MiG to repair fighter jets from its military aircraft fleet, Defense Minister Nikolay Nenchev has said.

In an interview with private national NOVA TV channel, Nenchev suggested the money might have been used either for "political purposes" or "hybrid warfare".

The development follows earlier reports about a letter sent by RSK MiG to the Bulgarian Parliament's Defense Committee to warn against intentions of the cabinet to perform maintenance activities in Poland - a country not officially authorized to repair MiGs.

The minister, for his part, insists the contract with RSK MiG, expiring this month, includes unfavourable conditions in terms of pricing and that by opting for Poland Bulgaria would save up to BGN 24 M. He also cites the risk for RSK MiG to enter an EU blacklist after the US took a similar step last year over the Ukraine crisis.

Commenting on the letter, Nenchev voiced his surprise at the fact that the letter was not addressed directly at him.

He noted the price it pointed was "two times lower" than what Bulgaria had been offered by MiG officials at their last meeting during talks to renew the contract earlier this year.

Over the past months, this has not been the first case of accusations thrown by Nenchev at RSK MiG. In April, he alleged to have been offered a bribe by company representatives if he chose to renew the maintenance contract. No evidence has yet been found.