Turkey is hosting the meeting, which was spurred by US President Donald Trump’s push for a quick deal to end the three-year war.

Zelensky, who previously voiced scepticism about the seriousness of the Russian side in proposing Monday’s meeting, said he had defined the Ukrainian delegation’s position going into it.

Priorities included “a complete and unconditional ceasefire” and the return of prisoners and abducted children, he said on social media.

Russia has said it has formulated its own peace terms but refused to divulge them in advance. Russian President Vladimir Putin ruled out a Turkish proposal for the meeting to be held at the leaders’ level.

Russian news agencies reported that the Russian delegation was scheduled to travel to Istanbul on Sunday for the talks.

The intensified strikes waged by each side came as Kyiv and Moscow each strived to show themselves coming from a position of strength.

A source with Ukraine’s SBU security service said the coordinated attacks inside Russia were “aimed at destroying enemy bombers far from the front”.

The source said Russian airbases in the eastern Siberian city of Belaya, in Olenya, up in the Arctic near Finland, and in Ivanovo and Dyagilevo, both east of Moscow, had been targeted.

More than 40 aircraft had been hit at the Belaya base, and a fire had broken out there, the source said, showing a video in which several aircraft could be seen in flames and black smoke rising.

AFP was not able to independently verify the claims or the video images.

Russia’s defence ministry confirmed on Telegram that several of its military aircraft “caught fire”, adding that there were no casualties and that several “participants” had been arrested.

Igor Kobzev, Governor of Russia’s Irkutsk region, which hosts the targeted Belaya airbase, said, “It’s the first attack of this sort in Siberia”.

He called on the population not to panic and posted an amateur video apparently showing a drone flying in the sky and a large cloud of grey smoke.

The governor of the Murmansk region, where the Olenya base was located, Andrey Chibis, also said “enemy drones” were flying overhead, and anti-aircraft defences were operating.

Russia has been announcing Ukrainian drone attacks on a near-daily basis, usually saying they had all been shot down. But it was rare for such drone strikes to be reported so deep within its territory.

At the same time, Russia has been carrying out constant attacks on Ukraine.

On Sunday, Ukraine’s air force said it was hit by 472 Russian drones and seven missiles overnight — a record since the beginning of the invasion.

In a rare admission of its military losses, the Ukrainian army said Russia’s “missile strike on the location of one of the training units” had killed a dozen soldiers, most of whom had been in shelters during the attack.

“As of 12:50 pm (0950 GMT), 12 people are known to have been killed and more than 60 wounded,” it said.

The attack led Ukrainian ground forces commander Mykhailo Drapaty to announce his resignation, saying he felt “responsibility” for the soldiers’ deaths.

Blasts Fell Bridges

Separately on Sunday, the Russian army said it had captured another village in Ukraine’s northern Sumy region, where Kyiv fears Moscow could mount a fresh ground assault.

Russia claims to have captured several settlements in the region in recent weeks and has amassed more than 50,000 soldiers on the other side of the border, according to Zelensky.

Authorities in the region have evacuated more than 200 villages amid intensified shelling.

Back in Russia, officials said a blast brought down a road bridge in the Bryansk region bordering Ukraine on Saturday, derailing a passenger train heading to Moscow and killing seven people.

A separate rail bridge in the neighbouring Kursk region was blown up hours later in the early hours of Sunday, derailing a freight train and injuring the driver.

Authorities did not say who was behind the explosions, but investigators said a criminal inquiry was underway.