Dutch wholesale gas prices reversed earlier gains on Thursday afternoon, amid ongoing uncertainty over the potential impact from demands for European buyers to pay for Russian gas in roubles and a weaker carbon market.

The Dutch day-ahead contract was down 1.60 euros at 89.40 euros per megawatt hour (MWh) by 1332 GMT, while the benchmark front-month contract for June delivery eased by 0.35 euros to 92.25 euros/MWh after hitting a low of 90.50 euros/MWh earlier.

"Volatility will remain extremely high the next couple of days and the market could go either way depending on what news come out regarding Russia and the rouble payment demands," analysts at Energi Danmark said in a note.

Given mild weather and a comfortable gas system, the market could be trading lower, a trader said.

It is widely expected that the first payments under a Russian decree demanding European clients pay for Russian gas deliveries in roubles are due on Friday but there is still uncertainty over whether companies could do so without breaching sanctions.

The European Union's executive told member states this week they can keep buying Russian gas without breaching sanctions imposed on Russia following its invasion of Ukraine, EU officials said but advised against opening a bank account in roubles.

Half of Russian gas giant Gazprom's 54 clients have opened accounts at Gazprombank, Deputy Prime Minister Alexander Novak said on Thursday, adding some big companies had already paid for Russian gas under the new scheme.

Russia has cut supplies to Poland and Bulgaria after a dispute over the rouble payment method, while Finland's Gasum, as smaller buyer of Russian gas refusing payment in roubles, is expecting deliveries to stop on Friday or Saturday.

In the British market, the day-ahead contract rose by 3.50 pence to 102.50 pence per therm, while the June contract eased by 1.53 pence to 175 pence/therm.

The UK system was 5 million cubic meters (mcm) oversupplied on Thursday despite a drop in Norwegian flows, which should remain curtailed due to maintenance, Refinitiv's analysts said in their morning report.

A bearish carbon market was also a factor in bringing gas prices down on Thursday, another trader said.

In the European carbon market, the benchmark contract traded down 2.72 euros at 81.92 euros a tonne.

Earlier in the day, it hit a three-week low of 80.16 euros/tonne, triggered by a weak auction European plans to raise 20 billion euros from selling extra permits.

(Reporting by Nora Buli in Oslo; editing by Nina Chestney)