Half a dozen balloons, apparently launched by Russia, were detected and shot down over the Ukrainian capital, Kyiv said on Wednesday.
The balloons could have been carrying reconnaissance equipment and were launched to “detect and exhaust our air defence forces”, Ukrainian authorities said.
“Most of the probes have been shot down,” the city's administration said in a statement. It added that authorities would carefully examine the debris.
The presence of the balloons in the sky prompted sirens to go off in the Ukrainian capital, which usually happens when missiles are approaching.
Ukrainian Air Force spokesman Yuriy Ignat said that Russia uses balloons to exhaust anti-aircraft missiles.
“The Russians will use all available methods of warfare to achieve their goals,” he told AFP.
“Therefore, it cannot be ruled out that these devices can conduct some kind of surveillance, so it is important to see what they are and understand them.”
Russia and Ukraine conflict latest — in pictures
Since the start of the Russian invasion last February, Ukrainian authorities have repeatedly reported Russian balloons drifting in the country's airspace.
On Tuesday, neighbouring Moldova temporarily closed its airspace due to the presence of a flying object resembling a weather balloon amid heightened tension with Moscow.
The US has been in a state of alarm since a huge white balloon from China was spotted over a series of top secret nuclear weapons sites before being shot down off the east coast.