KIEV, Jan. 16 – Ukrainian national oil and gas company Naftogaz Ukrayiny currently owes $650 million to RosUkrEnergo, Dmytro Firtash, a co-owner of the Swiss-registered gas trader, said on Echo of Moscow radio.

Problems with payments appeared in March last year when UkrGaz-Energo, a joint venture of RosUkrEnergo and Naftogaz Ukrayiny, was excluded from gas supply schemes, he said.

"Kiev has never re-exported Russian fuel," Firtash said.