European and UK gas prices jumped by as much as 24% this morning, to their highest this month, after Russian energy firm Gazprom claimed to have suspended gas flows to Poland and Bulgaria.
The firm had said on Tuesday that it would today stop gas reaching "unfriendly" nations that refuse to pay in roubles.
But Reuters now reports that gas to Poland was only cut briefly this morning, but later restored, while supplies to Bulgaria were flowing for the time being.
Unlike gas, the oil markets appear relatively calm this morning. Brent oil futures edged ahead by under 1% at $105.95 a barrel - still well short of the $120-plus price seen last month after Russia invaded Ukraine.
UK natural gas prices were at under 160p a therm on Tuesday, but hit 180p a therm this morning. However, this is still only around a third of the highs achieved in March.
Polish state gas company PGNiG relies on Gazprom for the majority of its gas imports, and bought 53% of its imports from the Russian company in the first quarter of this year.
It described the suspension move as a breach of contract, adding that the company would take steps to reinstate the gas supply.
Bulgaria, which uses Gazprom for more than 90% of its gas supply, said it had taken steps to find alternative sources but no restrictions on gas consumption were currently required.
The country's energy ministry said Bulgaria had fulfilled its obligations under the current contract with Gazprom and made all required payments.
It added that the new payment system proposed by Russia was in breach of the existing contract.
Poland's climate ministry said the country's energy supplies were secure.
Climate Minister Anna Moskwa said there was no need to draw gas from reserves, and gas to customers would not be cut.
Poland's Deputy Foreign Minister Marcin Przydacz said his country had been preparing for the possibility Russia might limit gas exports by diversifying its supplies.
"I'm pretty sure that we will manage to handle this," he told the BBC.
He added that the suspension proved Moscow was "not a reliable partner in any kind of business" and urged other European nations like Germany to support a ban on Russian energy imports.
Poland was already planning to stop importing Russian gas by the end of the year, when its long-term supply contract with Gazprom expires.
PGNiG said its underground gas storage was almost 80% full and, with summer approaching, demand was lower.
Poland also has alternative supply sources, including a liquefied natural gas (LNG) terminal in Swinoujscie.
On May 1, a new gas pipeline connection with Lithuania is also due to open that will give Poland access to gas from Lithuania's LNG terminal.
And a new pipeline delivering gas from Norway, known as the "Baltic Pipe", comes online in October. It should reach full capacity by the end of the year and could replace all Russian deliveries.