US President Donald Trump says Russia's Vladimir Putin has agreed not to attack Ukraine's capital Kyiv and other parts of the country for a week due to "extraordinary cold" weather.

Russia has not confirmed an agreement, but Ukraine's Volodymyr Zelensky welcomed the move.

While Trump did not specify when the pause would begin, overnight into Friday air raid alerts went off in just four Ukrainian regions that are close to the frontline.

Temperatures in Kyiv were due to plummet from Thursday and reach -24C (-11F) over the next few days. In recent weeks, Russia has intensified attacks on Ukraine's energy infrastructure, as it has during cold periods since the full-scale invasion began in 2022.

Ukraine's Air Force said on Friday that the four areas where sirens went off had been targeted by 80 Russian drones and a ballistic missile.

Speaking at a televised cabinet meeting in Washington DC on Thursday, the US president said: "I personally asked President Putin not to fire into Kyiv and the various towns for a week, and he agreed to do that."

"It was very nice. A lot of people said, 'Don't waste the call, you're not going to get that.' And he [Putin] did it," Trump added.

The Ukrainians, he said, "almost they didn't believe it, but they were very happy about it because they are struggling badly".

Later on Thursday, in a post on social media, Zelensky said Trump had made an "important statement" about "the possibility of providing security for Kyiv and other Ukrainian cities during this extreme winter period".

"Our teams discussed this in the United Arab Emirates (UAE). We expect the agreements to be implemented," he said.

The BBC understands that Ukraine has agreed to mirror Moscow's actions - pausing its own attacks on Russian oil refineries in response.

Last week, Russian, Ukrainian and US negotiators met in the UAE for the first trilateral talks since the war began.

All sides described the talks as constructive, but there has been no announcement that Russia had agreed to pause its attacks for the duration of the extreme cold currently gripping the region.

Instead, attacks have continued, crippling the power supply to major Ukrainian cities, leaving millions without heating or electricity.

Electrical companies carry out round-the-clock repairs, but their work can be quickly undone by Russian air attacks.

Even when power is restored, the supply only lasts a few hours - enough to charge appliances but not to substantially warm up homes.