Russia's largest government-affiliated gas company Gazprom says it has halted natural gas supplies to Poland and Bulgaria.

It is the first time Russia has closed off its gas pipeline since it started invading Ukraine.

Gazprom said on Wednesday it took the measure because Poland and Bulgaria have failed to pay for their procured natural gas in rubles.

The Russian government warned last month that gas contracts with states it deems unfriendly would be terminated if they refuse to pay in the Russian currency.

Bulgaria's energy minister told reporters on Wednesday his country has paid for Russian gas deliveries for April, so Gazprom would be in breach of contract if it halts the gas flow.

Poland, which procures more than half of its natural gas from Russia, stresses there would be no shortage of household gas supplies because it has been phasing out its reliance on Russia.

Russia's invasion of Ukraine has prompted European countries to procure gas from other sources. Some have decided to buy more liquefied natural gas from the Middle East and the US.

But it is unclear how they can deal with an abrupt halt in supplies like this one.