KYIV, Dec 14 - Ukrainian authorities said they thwarted a Russian attack on Kyiv and the surrounding region Wednesday as their air defense system destroyed 13 explosive-laden drones, although wreckage damaged five buildings, without causing casualties.

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 drones and missiles, and the possibility that Patriot missiles from the U.S. may further boost defenses.

President Volodymyr Zelensky said in a video the “terrorists” fired 13 Iranian-made drones, and all were intercepted, The Associated Press reported. Such drones have been part of the firepower — along with rockets, missiles, mortars and artillery — that Russia uses to target power stations, water facilities and other public utility equipment.

The snow-covered capital remained largely calm after the foiled 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.

A blast left the three-story tax office building in the central Shevchenkyvskyi district with a gaping hole in the roof and blew out windows in parked cars and in a neighboring building.

Clean-up crews were on site quickly to shovel away the rubble and roll out plastic sheeting to cover the blown-out windows in freezing temperatures. One man, unfazed, pushed his son on a swing set at a nearby playground as the crews worked.

Residents told Associated Press reporters they saw fragments from a drone bearing the words “For Ryazan.” The Kremlin claims Ukraine was responsible for a cross-border attack last week on a military base in the Ryazan region of western Russia.

Ukrainian authorities have trumpeted their ability to knock down Russian weapons. But strikes in some areas continue to cause deaths and havoc, particularly close to the front lines in the east and south. In the southern city of Odesa, drone strikes temporarily shut off the power last week. Kyiv has suffered comparatively little damage.

More air defense help was apparently on the way. U.S. officials said Tuesday the United States was poised to approve sending a Patriot missile battery to Ukraine, agreeing to an urgent Ukrainian request. The Patriot would be the most advanced surface-to-air missile system the West has provided to Ukraine to help repel Russian aerial attacks since Russia invaded Feb. 24.

U.S. officials said last week that Moscow has looked to Iran to resupply its military with drones and surface-to-surface missiles.

The damage from Russian strikes has interrupted electricity, heating and water supplies as winter approaches. Yet the U.N. migration agency said more than 5 million people who were displaced within or outside Ukraine since Russia invaded have returned. The International Organization for Migration said a Nov. 25-Dec. 5 phone survey of 2,002 respondents in Ukraine found that only 7% were considering leaving. (ap/ez)