STOCKHOLM, October 9. /TASS/. The Svea District Court of Appeal in Sweden started substantive hearing of the appeal filed by the Russian gas holding Gazprom against the award of the Stockholm Arbitration in the gas transit dispute with Naftogaz of Ukraine, the Court told TASS on Wednesday.

"The substantive hearing of the Gazprom case has started today. A portion of data in this case is classified," the Court noted.

The last hearing will take place on October 17. It is impossible to say when the decision in the case will be made, the Court’s spokesperson said earlier.

Preliminary hearing ended on November 27 of the last year.

Gazprom and Naftogaz are in litigation on contracts for gas transit and supply to Ukraine since 2014. In February 2018, the Stockholm Arbitration ordered the Russian company to pay $2.56 bln for insufficient supply of transit gas.

Gazprom challenged these decisions and later sought complete cancellation of the ‘transit’ decision. The appeal of Gazprom against the arbitration decision on gas supplies was planned for review in October 2019, as reported earlier.

The two contracts signed in 2009 by Gazprom and Naftogaz on gas supplies to Ukraine and on gas transit through the country to Europe will expire at the turn of 2019-2020.