Ukraine has said it destroyed more than 40 Russian bomber planes at a number of military airbases in Russia.

BBC said this was confirmed by sources from Ukraine's security service, SBU.

The report stated that strategic bombers were "burning en masse" in an operation named "Spider's Web", personally overseen by President Volodymyr Zelensky.

The sources said it took a year-and-a-half to organise the strikes: drones hidden in wooden mobile cabins with remotely opening roofs had been placed on trucks brought near the airbases and then fired "at the right time".

Russia's military later confirmed Sunday's Ukrainian attacks in five regions calling them a "terrorist act".

Meanwhile, Ukrainian authorities have reported a massive overnight drone and missile attack on its territory.

All this comes as Russian and Ukrainian negotiators are heading to Istanbul, Turkey, for a second round of peace talks on Monday.

Expectations are low, as the two warring side remain far apart on how to end the war.

Russian President Vladimir Putin launched a full-scale invasion of Ukraine in February 2022.

Moscow currently controls about 20% of Ukrainian territory, including southern Crimea peninsula annexed in 2014.

Russia later said it faced attacks across sites in five regions.

The SBU sources said that among the hit Russian aircraft were strategic nuclear capable bombers called Tu-95 and Tu-22M3, as well as A-50 early warning warplanes.

They described the whole operation as "extremely complex logistically".

"The SBU first smuggled FPV drones into Russia, followed later by mobile wooden cabins. Once on Russian territory, the drones were hidden under the roofs of these cabins, which had been placed on cargo vehicles," the sources said.

"At the right moment, the roofs were remotely opened, and the drones took off to strike the Russian bombers."

Irkutsk Governor Igor Kobzev confirmed drones that attacked the Belaya military base in Sredniy, Siberia, were launched from a truck.

Kobzev posted on Telegram to say that the launch site had been secured and there was no threat to life.

Russian media outlets have also reported that other attacks were similarly started with drones emerging from the lorries.

One user is heard saying that the drones were flying out of a Kamaz truck near a petrol station.

The BBC sources in the SBU said that "preliminary estimates suggest that the damage inflicted on Russian aviation exceeds $2bn (£1.5bn)".

Russian media were reporting the attack in Murmansk but said air defences were working. The attack in Irkutsk was also being reported.

In a post on social media later on Sunday, the Russian defence ministry confirmed that airbases in the country's five regions were attack.