Ukrainian state energy firm Naftogaz said on Tuesday it had transferred $1.45 billion to Russia's Gazprom, the first tranche of debt repayment required by an agreement that will see Moscow resume gas supplies to its ex-Soviet neighbor.

Last week Moscow, Kiev and the European Union clinched a deal in Brussels that would restart supplies of Russian gas to Ukraineover the winter in return for payments funded in part by the Ukrainian government's Western backers.

Worth $4.6 billion in total, the package calls for Ukraine to pay $3.1 billion in two tranches by the end of the year to cover debts for previous supplies from Gazprom, which cut off gas to Ukraine in June.

Naftogaz said it would pay the $3.1 billion, but stressed that the latest deal with Gazprom was only temporary - both companies have lodged cases with the Stockholm arbitration tribunal to review their gas transit contracts.

"The Brussels agreements are temporary solutions and do not affect the positions of the parties in court," Naftogaz said in a statement.

On Friday Gazprom head Alexei Miller said Russia would restart gas supplies to Ukraine as soon as Ukraine repaid the first debt tranche, as well as $760 million up front for November supplies.

Naftogaz did not refer to a payment for November gas in its statement on Tuesday.