KYIV: Ukraine said Wednesday its aerial defence units had detected half a dozen balloons, apparently launched by Russia, over the capital Kyiv and shot most of them down.

Kyiv authorities said the balloons could carry reconnaissance equipment and were launched to "detect and exhaust our air defence forces."

"Most of the probes have been shot down," the city administration said in a statement, adding 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 troops 'firmly holding' Bakhmut: Zelensky

Ukrainian Air Force spokesman Yuriy Ignat said that Russia uses balloons to exhaust Ukrainian 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."

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 tensions with Moscow.

The United States has been in a state of alarm since a huge white balloon from China was spotted tracking over a series of top secret nuclear weapons sites, before being shot down off the east coast in early February.