Fierce fighting continued in parts of Ukraine and Russia on Sunday — mere hours before leaders from the two countries were set to meet for peace talks in Turkey. Kyiv destroyed more than 40 planes deep inside Russian territory on Sunday during an “extremely complex” operation that took more than a year of planning. The Security Service of Ukraine said Operation Web had wiped out 34% of the Russian fleet of air missile carriers with damages estimated at $7 billion.

Ukrainian President Volodymyr Zelensky said 117 drones had been used in the operation and headquartered out of an office next to the local FSB headquarters. The FSB is the Russian intelligence and security service. An official told Associated Press that the far-reaching attack was personally supervised by Zelensky and took more than a year and a half to execute. The military source also explained that the operation had begun with the smuggling of first-person view drones to Russia. They were then placed in mobile wooden houses.

“Later, drones were hidden under the roofs of these houses while already placed on trucks. At the right moment, the roofs of the houses were remotely opened, and the drones flew to hit Russian bombers,” the source said.

Social media footage shared by Russian media appeared to show the drones rising from inside containers while other panels lay discarded on the road. One clip appeared to show men climbing onto a truck in an attempt to halt the drones.

The drones reportedly hit 41 planes stationed at military airfields on Sunday afternoon, including A-50, Tu-95 and Tu-22M aircraft. Moscow has previously used Tupolev Tu-95 and Tu-22 long-range bombers to launch missiles at Ukraine, while A-50s are used to coordinate targets and detect air defenses and guided missiles.

The Russian Defense Ministry confirmed the attacks in an official statement — noting that it had damaged aircraft and sparked fires on air bases in the Irkutsk region (more than 4,000 kilometers from Ukraine) as well as the Murmansk area in the north. Russia’s top investigative body said that explosions had caused two bridges to collapse and derailed two trains in western Russia overnight, killing seven in one of the incidents and injuring dozens more. Russian officials, however, did not say what had caused the blasts and the word “explosions” was later removed from an Investigative Committee press release.

(With inputs from agencies)