Russia unleashed waves of air strikes on Kyiv overnight in what officials said appeared to be the largest drone attack on the city since the start of the war, as the Ukrainian capital prepared to celebrate the anniversary of its founding on Sunday.

Ukraine’s Air Force said it downed 52 out of the 54 Russia-launched drones, calling it a record attack with the Iranian-made ‘kamikaze’ drones. It was not immediately clear how many of the drones were shot over Kyiv.

In what also appears to be the first deadly attack on Kyiv in May and the 14th assault this month, falling debris killed a 41-year-old man, Mayor Vitali Klitschko said.

The pre-dawn attacks came on the last Sunday of May when the capital celebrates Kyiv Day, the anniversary of its official founding 1,541 years ago. The day is typically marked by street fairs, live concerts and special museum exhibitions — plans for which have been made this year too, but on a smaller scale.

“The history of Ukraine is a long-standing irritant for the insecure Russians,” Andriy Yermak, the head of President Volodymyr Zelenskiy’s office, said on his Telegram channel.

Air Force said on Telegram that Russia had targeted military and critical infrastructure facilities in the central regions of Ukraine, and the Kyiv region in particular.

Reuters was unable to independently verify the information.

With a Ukrainian counteroffensive looming 15 months into the war, Moscow has intensified air strikes after a lull of nearly two months, targeting chiefly military sites and supplies. Waves of attacks now come several times a week.

The Sunday attacks came after Kyiv said that combat clashes eased around the besieged city of Bakhmut in southeastern Ukraine, the site of the war’s longest battle.

Serhiy Popko, the head of Kyiv’s military administration, said the attack was carried out in several waves, and air alerts lasted more than five hours.

“Today, the enemy decided to ‘congratulate’ the people of Kyiv on Kyiv Day with the help of their deadly UAVs (unmanned aerial vehicles),” Popko said on the Telegram messaging channel.

Several districts of Kyiv, by far the largest Ukrainian city with a population of around three million, suffered in the overnight attacks, officials said, including the historical Pecherskyi neighbourhood.

Reuters witnesses said that during the air raid alerts that started soon after midnight, many people stood on their balconies, some screaming offensives directed at Russia’s President Vladimir Putin and “Glory to air defence” slogans.

In the leafy Holosiivskyi district in the southwestern part of Kyiv, falling debris set a three-storey warehouse on fire, destroying about 1,000 square metres of building structures, Mayor Klitschko said.

A fire broke out after falling drone debris hit a seven-storey non-residential building in the Solomyanskyi district west of the city. The district is a busy rail and air transport hub.

In the Pecherskyi district, a fire broke out on the roof of a nine-storey building due to falling drone debris, and in the Darnytskyi district a shop was damaged, Kyiv’s military administration officials said on Telegram.