MOSCOW, March 30. /TASS/. The repair and upgrade of Russian-made helicopters with their subsequent transfer to Ukraine are a gross violation of international commitments undertaken by the Czech Republic and Bulgaria, Russia’s Federal Service for Military-Technical Cooperation told TASS on Thursday.

Pursuant to media reports, the Bulgarian state-owned companies Avionams and Terem-Letec and the Czech firm Lom Praha continue the illegitimate activity for the repair and upgrade of Soviet-and Russian-made combat helicopters for their subsequent delivery to Ukraine, the Federal Service said.

"The above-mentioned activity carried out by Bulgaria and the Czech Republic is a gross violation of international commitments and inflicts considerable damage on the world export control system," the Federal Service for Military-Technical Cooperation said.

The Russian side bears no responsibility for the safe operation of helicopters serviced by these companies without the participation of Russian producers and the firm that engineered this equipment, it stressed.

In July last year, Russia suspended the certificates issued to the Czech state-owned enterprise Lom Praha and the Bulgarian companies Terem-Letec and Avionams. The companies were stripped of the right to carry out maintenance or repair of Russian helicopters.