Ukraine has stopped the flow of Russian natural gas through a hub that feeds European homes, while Kyiv's military claimed it has made some gains in grinding battles near a key north-eastern city.

In 11 weeks, the war has played out on battlefields in Ukrainian towns and cities but also in energy and financial markets, as Ukraine's allies in the West have sought to deprive Russia of money needed to fund the war with sanctions and energy embargoes.

The practical impact of Wednesday's gas cut-off for European households was not immediately clear: Ukraine's pipeline operator said it would switch supply to another hub, and an analyst said transit should not be affected.

But Russia's state-owned giant Gazprom indicated some fall-off - it said it was sending gas supplies to Europe through Ukraine in the amount of 72 million cubic metres, apparently down 25% from the day before.

Preliminary flow data suggested higher rates moving through a second station in Ukrainian-controlled territory.

Russian gas flows to Europe through other pipelines as well.

It was also not clear if Russia would take any immediate hit, since it has long-term contracts and other ways of transporting gas.

But the move could hold symbolic significance as the first time Ukraine has disrupted the flow westward.

It comes as the European Union has sought to reduce its dependence on Russian energy, phasing out its use of coal and considering doing the same for oil.

Gas presents a more complicated problem, given both how much Europe uses and the technical difficulties in sourcing it elsewhere.

On the battlefield, President Volodymyr Zelensky said Ukraine's military had pushed Russian forces out of four villages near Kharkiv - the country's second largest city, and a key to Russia's offensive in the eastern Donbas.

After his forces failed to overrun the capital Kyiv in the early days of the war, Russian President Vladimir Putin switched his focus to the region, which is Ukraine's industrial heartland and has also been the site of fighting between Moscow-backed separatists and Ukrainian troops for years.

Mr Zelensky suggested the military was gradually pushing Russian troops away from Kharkiv.

As his forces appear to gather steam in a nascent counteroffensive, foreign minister Dmytro Kuleba voiced what appeared to be increasing confidence - and expanded goals - on Tuesday.

He suggested to the Financial Times newspaper that Ukraine could go beyond just forcing Russia back to areas it held before the invasion began 11 weeks ago.

Mr Kuleba's statement seemed to reflect political ambitions more than battlefield realities: Russian forces have made advances in the Donbas and control more of it than they did before the war began.

But it highlights how Ukraine has stymied a larger, better-armed Russian military, surprising many who had anticipated a much quicker end to the conflict.

Meanwhile, the British Ministry of Defence said Ukraine was targeting Russian forces on Snake Island in the north-western Black Sea, in an effort to disrupt Moscow's attempts to expand its influence.

Russia has sought to reinforce its garrison on Snake Island, while "Ukraine has successfully struck Russian air defences and resupply vessels with Bayraktar drones", the MoD said on Twitter.

It said Russian resupply vessels had minimum protection after the Russian navy retreated to Crimea after losing the flagship of its Black Sea fleet.

Satellite photos analysed by the Associated Press show fighting there.

But the statement warned: "If Russia consolidates its position on (Snake) Island with strategic air defence and coastal defence cruise missiles, they could dominate the north-western Black Sea."

Ukraine's natural gas pipeline operator said it would stop Russian shipments through a hub in a part of eastern Ukraine controlled by Moscow-backed separatists because of interference from "occupying forces", including the apparent siphoning of gas.

It also complained about interference along the route last month.

Benchmark European gas futures seesawed on Tuesday and Wednesday on the news, meaning consumers may face higher energy bills - at a time of already rising prices.

Higher prices would benefit Russia, though it has massive foreign reserves now given the rapid rise in crude oil prices in recent months as global travel and business resumed in the wake of mass coronavirus pandemic lockdowns.

The hub in question handles about a third of Russian gas passing through Ukraine to western Europe.

Russia's state-owned natural gas giant Gazprom put the figure at about a quarter.

The move came as western powers have been looking to ratchet up economic pressure on Moscow and bolster Ukraine's defenders.

The US House of Representatives approved a 40 billion dollar (£32 billion) Ukraine aid package on Tuesday.

On Wednesday, Ukrainian officials said a Russian rocket attack targeted an area around Zaporizhzhia, destroying unspecified infrastructure.

There were no immediate reports of casualties.

The south-eastern city has been a refuge for many civilians who have fled a Russian siege in the devastated port city of Mariupol.

With much of the fighting focused in the east, some analysts suggested Russia may be trying to spread Kyiv's forces thin, by striking the southern port of Odesa, a major gateway for grain that feeds the world as well as a key transit point for western weapons.

Russia targeted the city with several missile strikes this week, the Ukrainians said on Tuesday.

To protect Odesa, Kyiv might need to shift forces to the south-west, drawing them away from the eastern front in the Donbas, where they are fighting near Kharkiv to push the Russians back across the border.

Russian aircraft twice launched unguided missiles on Tuesday at the Sumy area north-east of Kharkiv, according to the Ukrainian border guard service.

The region's governor said the missiles hit several residential buildings, but no-one was killed.

Russian mortars hit the Chernihiv region, along the Ukrainian border with Belarus, but there was no word on casualties.