The Nord Stream 1 gas pipeline linking Russia to Germany has restarted after ten days of maintenance work, its operator has said.
"It's working," a Nord Stream spokesman said, without specifying the amount of gas being delivered.
The German government had feared the pipeline would not be reopened by Russia after the scheduled work.
The pipeline transports 55 billion cubic metres (bcm) a year of gas under the Baltic Sea and has been offline for annual maintenance since 11 July.
On the operator Nord Stream AG's website, physical flows were at 21,388,236 kwh/h for 5-6am Irish time, from zero previously.
The resumption in gas flows could take several hours, a spokesperson for the operator has said.
A spokesperson for Austria's OMV said Gazprom signalled it would deliver around 50% of agreed gas volumes today, levels seen before the shutdown.
German pipeline manager Gascade has previously said it expected Russian gas deliveries to resume at 40% of capacity, the level of supplies before maintenance work.
Yesterday, the European Commission urged EU countries to reduce demand for natural gas by 15% over the coming months to secure winter stocks and defeat Russian "blackmail".
EU commissioners also asked member states to give Brussels special powers to impose compulsory energy rationing if Russia cuts off Europe's gas lifeline.
Last year, Russia represented 40% of the EU's total gas imports and any further disruption to supply would also push consumer prices higher and raise the risk of a deep recession.
"Russia is blackmailing us," European Commission President Ursula von der Leyen told reporters.
"Russia is using energy as a weapon and therefore, in any event, whether it's a partial major cut off of Russian gas or total cut off... Europe needs to be ready."
Russia, the world's largest gas exporter, has denied accusations of using its energy supplies as a tool of coercion, saying it has been a reliable energy supplier.
A Kremlin spokesperson said gas delivery problems to Europe were caused by sanctions that create "technical difficulties".
"Any technical difficulties linked to this are caused by those restrictions that European countries introduced themselves," Kremlin spokesman Dmitry Peskov told reporters.
He said accusations that Russia was using gas deliveries as political blackmail were "completely" unfounded.
