Donald Trump has claimed that Russia and Ukraine have agreed to an "energy ceasefire", with Kyiv saying it would support such a move but Moscow yet to comment.

The US president insisted that it was "effective immediately" but provided no details.

Ukrainian President Volodymyr Zelensky initially expressed surprise at the announcement, before saying Kyiv would support it if Moscow did. He also accused Russia of striking Ukrainian energy facilities after Trump's post.

Trump has been urging Ukraine to stop strikes on Russian oil infrastructure – which Kyiv says are vital to curtailing revenue for Moscow's war machine – so Russia can fulfil a recently-struck deal to release diesel to the US and the global market.

The diesel deal, temporarily undoing sanctions on Russian imports, is attracting growing criticism. Zelensky called it a gift to Russian President Vladimir Putin. European officials and some US politicians, including from Trump's Republican party, have said they do not support it.

The deal is Trump's latest effort to lower domestic fuel prices ahead of the midterm elections, having spent months grappling with the political consequences of the war with Iran which has pushed up global fuel prices, particularly those for diesel.

That has soured Trump's standing with the American public, who have been stung by the higher pump prices and knock-on effects that led to across-the-board inflation.

Zelensky said it was "news" to him that an energy truce was in effect in comments to news site Axios, before writing on social media that his officials "look forward to clear details of America's dialogue with Russia".

"Ukraine is ready not to strike at Russian energy and we count on Russia's similar readiness and on the agreement of the president of the United States of America on this," he said.

The BBC has asked the White House for further details.

UK Prime Minister Andy Burnham said Britain "strongly supports President Trump's call today for a sustained energy ceasefire to start now", while France, Canada and the EU also expressed support.

Zelensky later said Russia had hit a power plant in Kyiv with a drone, causing power cuts, followed by strikes on energy facilities in the north-eastern Kharkiv region.

"All of this happened after the president of the United States made his statement about an energy ceasefire," he said.

For months, Ukraine and Russia have been exchanging strikes on energy infrastructure.

Moscow said the installations it hits were legitimate targets because they supported Ukraine's military operation, while Zelensky has characterised Ukrainian attacks deep inside Russian territory as part of an effort to "reduce Russia's ability to finance the war".

The attacks have disrupted energy supplies on both sides.

Earlier on Sunday, UK Defence Secretary Wes Streeting told the BBC that the UK did not support it, while EU foreign policy chief Kaja Kallas echoed Zelensky's criticism of it on Saturday.

The deal has also attracted criticism from politicians of both main US parties.

Seven senators, including three Democrats and four Republicans, have published a statement saying Trump's deal "runs directly counter" to a law that had explicitly banned Russian energy imports.

"Congress was clear: the US should not import oil from Russia until it ends its aggression against Ukraine and ceases threats against our Nato Allies," they said, urging the Trump administration to "reverse course".

Republican Senator Thom Tillis, one of the seven, told NBC News that the deal "absolutely will" put American lives at risk.

On Saturday Trump accused Zelensky of wanting to "make problems for the world" by continuing to authorise attacks on Russian refineries following the Ukrainian leader's criticism of the diesel deal.

The US president suggested that it was "time for Ukraine to get a new president".

Zelensky pledged to hold elections – despite them being suspended by the Ukrainian constitution during wartime – if Russia agreed to a 60-day total ceasefire.

The Ukrainian president previously resisted calls from the US for fresh elections, pointing to complications with holding a vote in parts of the country that are active war zones or under Russian occupation.

Trump, however, has repeatedly accused the Ukrainian leader of using the war to stay in power.

Meanwhile, strikes and fighting on the ground continue in the four-year-long war.

Six people were killed in attacks on two Ukrainian cities on Sunday, regional officials said.

One person was killed in Russia's Belgorod region, which borders Ukraine, while another man was killed in a drone attack in the Russian-occupied Donetsk region, officials said.