Italy's Eni said it would not receive any of the gas it had ordered from Russia's Gazprom for delivery this weekend, although the firms said they were working to fix this.
Russian gas supplies through the Tarvisio entry point will be at zero for Oct. 1, Eni, the biggest importer of Russian gas in Italy, said in a statement on its website on Saturday.
The Italian group later added that it would not receive any of the requested imports for Oct. 2, and that the situation was expected to remain the same into Monday.
Moscow and several European countries, including Germany, have been at loggerheads over the supply of natural gas from Russia since the country's invasion of Ukraine in February.
Tensions soared this week after leaks in the Nord Stream 1 and 2 pipelines linking Russia and Germany spewed tons of methane into the Baltic Sea, in what the United Nations believes could be the largest leak of the climate-damaging gas ever recorded.
On Saturday, the operator of Nord Stream 2 said gas had finally stopped leaking out, five days after the initial rupture, which both Russia and the West blamed on sabotage.
The European Union says Moscow is using the flow of gas needed for energy in the region as an economic weapon, something that Russia has consistently denied, blaming instead the impact of Western sanctions for any disruptions in supply.
Gazprom said in a statement on Telegram the problem was the result of regulatory changes in Austria. It said gas transit through the country had been suspended after its grid operator refused to confirm transport nominations or the amount Gazprom planned to ship.
The Austrian government said Gazprom had not signed the contracts needed.
"At the beginning of each gas year, various technical changes in the market model come into force," the energy ministry said in a statement. "Contractual changes are necessary for this. These contracts have not yet been signed by Gazprom. Transport nominations for today could therefore not be accepted. A solution is currently being worked on at the technical level at full speed."
A spokesperson for Eni said Austria continued to receive gas on its border with Slovakia.
A spokesperson for Austria's OMV said supplies from Russia were not an issue. "The volumes nominated for today's gas day were significantly higher for OMV today than of late," he said.
Italy has secured additional gas imports this year from alternative suppliers to make up for a fall in flows from Russia after the start of the war in Ukraine.
Russian gas now accounts for around 10% of Italian imports, down from around 40%, a source close to the matter said, while the share from Algeria and the Nordics has increased.
Elsewhere, Gazprom cut natural gas supplies to Moldova by around 30%, Vadim Ceban, director of gas firm Moldovagaz, said.
On Friday, Moldova's Deputy Prime Minister Andrei Spinu said Gazprom had warned it about the reduction.
Spinu said on Saturday that technical problems caused the reduction and Moldova would ask Gazprom to increase supplies.
