Russia's state-owned gas company on Monday announced an unexpected, drastic cut in supply to Europe, leading Ukraine to call the West to action over the "gas war".

The gas cuts came amid guarded hope of resuming exports this week of another key commodity -- Ukraine's grain -- under a breakthrough deal that was called into question by a strike by Moscow on the key port of Odessa.

Gazprom, the Russian energy giant, said it was cutting daily deliveries of gas to Europe via the Nord Stream pipeline to 33 million cubic metres a day -- about 20 percent of the pipeline's capacity -- from Wednesday.

Russia also pursued an artillery campaign over Ukraine's second city, Kharkiv
Russia also pursued an artillery campaign over Ukraine's second city, Kharkiv AFP / SERGEY BOBOK

The company said it was halting the operation of one of the last two operating turbines due to the "technical condition of the engine".

But Germany -- which is heavily reliant on Russian gas but has looked to wean itself off gradually following Moscow's February 24 invasion of Ukraine -- said there was no technical justification for the cut.

German group Siemens Energy, which is charged with maintaining the turbine, also said in a statement to AFP that it saw "no link between the turbine and the gas cuts that have been implemented or announced".

Ukrainian President Volodymyr Zelensky said that the cuts showed that Europe should bolster sanctions against Russia.

After earlier denying carrying out the strikes on Odessa, Russia claimed its missiles had destroyed Western-supplied arms
After earlier denying carrying out the strikes on Odessa, Russia claimed its missiles had destroyed Western-supplied arms Odessa City Council Telegram channel via AFP / STR

"This is an open gas war that Russia is waging against a united Europe," Zelensky said.

"They don't care what will happen to the people, how they will suffer -- from hunger due to blocked ports, from winter cold and poverty... or the occupation. These are just different forms of terror," he said in his daily video message.

"That is why you have to hit back. Do not think about how to bring back the turbine, but strengthen the sanctions," he said.

The Russian announcement came on the same day that Ukraine announced receiving the first of an expected 15 Gepard anti-aircraft systems and tens of thousands of shells from Germany.

Main ports in Ukraine's Black Sea region
Main ports in Ukraine's Black Sea region AFP / Emmanuelle MICHEL

Russia and Ukraine on Friday concluded their most significant agreement since the start of the war, signing a deal brokered by Turkey and the United Nations to release some 25 million of tonnes of wheat and other grain that had been trapped in Ukraine's Black Sea ports.

The agreement in Istanbul has brought little reprieve on the battlefield where Russian forces were carrying out bombardments across the sprawling front line
The agreement in Istanbul has brought little reprieve on the battlefield where Russian forces were carrying out bombardments across the sprawling front line AFP / Igor TKACHEV

The breakthrough raised hopes of relieving a spike in global food prices that has hit poor nations hardest. But less than 24 hours later, Moscow struck the port in Odessa -- one of three exit hubs designated in the agreement.

Ukraine voiced fury but said Monday that it still expected implementation of the deal in the coming days.

"We are preparing for everything to start this week," Ukraine's infrastructure minister Oleksandr Kubrakov, who led Ukraine's delegation at last week's grain talks in Istanbul.

Ukrainian officials said the port of Chornomorsk in southwestern Ukraine would be the first to be opened and insisted on the importance of security following the strike on nearby Odessa.

Russia has insisted that its strikes on Ukraine's port of Odessa 'should not affect' the Turkish-brokered push to send grain to world markets
Russia has insisted that its strikes on Ukraine's port of Odessa 'should not affect' the Turkish-brokered push to send grain to world markets AFP / BULENT KILIC

Russia had justified its blockade in part due to mines, which Ukraine said were necessary to prevent an amphibious assault.

Kubrakov said de-mining will take place only in the shipping lanes required for grain exports, while Ukrainian ships will accompany the departing convoys that will transport not only grain but also fertiliser.

After speaking to Kubrakov by phone, Turkish Defence Minister Hulusi Akar welcomed Ukraine's resolve to resume the shipments.

"It is important that the first ship starts sailing as soon as possible," Akar said in a statement.

The Kremlin insisted Monday that its strikes in Odessa, which it initially denied to Turkey, "should not affect" the Turkish-brokered push to send the grain to world markets.

Spokesman Dmitry Peskov said Moscow's cruise missiles hit "exclusively" military infrastructure and were "not connected with the agreement on the export of grain."

Russia has looked to shift the blame for the food crisis onto Western sanctions. Foreign Minister Sergei Lavrov was visiting Africa where on his first stop, Egypt, he promised that Russia would meet grain orders.

Ukrainian presidential aide Mykhaylo Podolyak slammed the visit as a cynical ploy by Moscow after it had fuelled the food crisis.

"You arranged the artificial hunger and then come to cheer people up," he said on Twitter, assuring that Ukrainian grain will reach its destinations.

In Washington, State Department spokesman Ned Price voiced hope that grain shipments would come out in the coming days but said the United States was "clear-eyed".

"Moscow's track record when it comes to previous deals that it has struck is not exactly a cause for optimism," Price said.

Russia is pressing on with a grinding push across Ukraine's southeast, where Kyiv's forces are being boosted by fresh Western military aid shipments.

The Ukrainian presidency said Monday that a Russian strike trapped seven people under the rubble of a collapsed cultural centre in the northeastern Kharkiv region. Three were pulled out alive and the rescue operation was ongoing.

It reported shelling across the entire front line and at least one person was killed in the town of Soledar.

Ukraine's bid to oust the Kremlin's forces has been bolstered by longer range Western weapons that have allowed Kyiv to target Russian supply lines deeper in occupied areas.