The head of the city’s military administration had said that the flash was caused by a Nasa satellite returning to Earth.

But a Nasa spokesman said that this was not the case as the satellite in question was “still in orbit”.

“We cannot identify what it was exactly, but our assumption is that it was a meteorite,” Igor Korniyenko, the deputy head of a control centre at Ukraine’s national space agency said today.

But he said there was not sufficient data to determine “the exact nature” of what might have caused the flash.

“Our observation devices showed it was a powerful explosion. We recorded it and determined where it took place,” he said.

The US space agency had announced earlier this week that a retired 660-pound satellite would re-enter the atmosphere some time yesterday.

“What exactly it was – only experts can find out,” the military administration’s chief Sergiy Popko said today.

But he ruled out that the flash could have been one of the regular Russian missile and drone strikes on the Ukrainian capital since Russia attacked the country in February 2022.

Speculation and memes abounded on Ukrainian social media, including jokes that the mysterious flash could have been caused by an alien spacecraft.