(QHA) -

Naftogaz of Ukraine has also filed a lawsuit at the Stockholm arbitration court against Gazprom, the company's press service informs.

"National Joint-Stock Company Naftogaz of Ukraine has filed a lawsuit at the Arbitration Institute of the Stockholm Chamber of Commerce. The company is demanding the establishment of a fair and market-oriented price for gas, which OJSC Gazprom supplies to Ukraine," the company said.

It added that the lawsuit also contains the demand to collect from Gazprom overpayment for the gas supplied by Russia's monopoly in 2010. 

"Such overpayment estimated at $6 billion," - Naftogaz noted.

To recall, Gazprom switched Ukraine to pre-payment for gas from 09.00 on Monday, and filed a lawsuit at the Stockholm arbitration with the demand that Naftogaz repay $4.5 billion in debt.