Ukrainian authorities said they thwarted a Russian attack on Kyiv and the surrounding region Wednesday as their air defense system intercepted and destroyed 13 explosive-laden drones, although wreckage from some of them damaged five buildings. No casualties were reported.

The attempted strikes underlined how vulnerable Ukraine’s capital remains to the regular Russian attacks that have devastated infrastructure and population centers in recent weeks, mostly in the country’s east and south. But they also highlighted Ukraine’s claims of increasing efficiency in intercepting weapons – something that Patriot missiles from the U.S. may soon help boost.

Ukrainian President Volodymyr Zelenskyy, in a brief video statement, said the “terrorists” fired 13 Iranian-made drones, and all were intercepted. Such drones have been part of the firepower, along with rockets, missiles, shelling mortars and artillery, as Russia targets power stations, water facilities and other public utility sites.

The snow-covered capital remained largely calm after the attack, which occurred around daybreak. As the working day began, authorities sounded the all-clear.

The head of the Kyiv city administration, Serhii Popko, wrote on Telegram that the attempted strikes came in two waves. Wreckage from the intercepted drones damaged an administrative building and four residential buildings, he said.