Poland's dominant gas company PGNiG said its biggest supplier, Russia's Gazprom , had proposed increasing prices for its gas in an existing long-term delivery deal, at a time of heightened tensions between Moscow and Warsaw.

State-run PGNiG, which has said it will not renew the deal that runs until 2022, said in its statement late on Monday that the proposal to renegotiate the price was groundless.

Gazprom's exporting arms, Gazprom Export, confirmed on Tuesday it had sent a proposal to PGNiG to review the gas price upwards starting from November 2020.

PGNiG, which earlier this month asked Gazprom to lower the delivery price, imports most of the gas it resells from Gazprom based on the existing long-term deal.

Poland has sought to reduce reliance on Gazprom.

Gazprom and PGNiG have had a long-running dispute over gas prices. PGNiG has repeatedly said it pays more than its European peers for Gazprom's gas.

In a flare up of a wider political row, Poland fined Gazprom more than 29 billion zlotys ($7.6 billion) for building the Nord Stream 2 gas pipeline without Warsaw's approval.