A mysterious flash that lit up the skies over the Ukrainian capital Kyiv generated much speculation.
Ednews reports citing BBC that officials in Kyiv said they suspected it was a Nasa satellite falling to Earth but the US space agency told the BBC it was still in orbit.
The Ukrainian air force suggested the flash might have been a meteorite.
Whatever it was, the air force seemed confident it had not been caused by a Russian air attack - an event all too familiar since the invasion last year.
The bright glow was observed in the sky over the capital around 22:00 (19:00 GMT).
An air raid alert was activated but "air defence was not in operation", the head of Kyiv's military administration, Serhiy Popko, said on Telegram.
"According to preliminary information, this phenomenon was the result of a Nasa space satellite falling to Earth," Mr Popko said.
The US space agency had announced earlier this week that a retired 660-pound (300-kg) satellite would re-enter the atmosphere on Wednesday.
The RHESSI spacecraft, used to observe solar flares, was launched into low Earth orbit in 2002 and decommissioned in 2018, Nasa said.
But Rob Margetta from Nasa's Office of Communications told the BBC that the satellite was still in orbit at the time the flash was observed, and would re-enter Earth's atmosphere during the night.
Nasa and the US defence department continued to track RHESSI, he added.
Ukrainian social media has been awash with theories and memes about what the flash could have been, with a popular theme being that it was caused by aliens.
