LISBON (Reuters) - A bright comet fragment lit up the skies over parts of Spain and Portugal late on Saturday, according to the European Space Agency (ESA), with one Lisbon resident saying the dazzling display "felt like a movie".

On Sunday morning, the ESA shared on X a video captured by its "fireball camera" of what it described as a "stunning meteor" over the skies of the western Spanish city of Caceres, near the Portuguese border.

But it later said it appeared to be a "small piece of a comet" and not a meteor, estimating it flew over Spain and Portugal at a speed of 45 km (28 miles) per second before burning up over the Atlantic.

"The likelihood of any meteorites being found is very low," the ESA said.

In both countries, videos shot in several cities and towns went viral on social media, showing the object crossing the night sky at high speed and illuminating it in bright tones of blue and green.

The Spanish Calar Alto astronomical observatory also said a preliminary analysis by Andalusia's Institute of Astrophysics revealed the object had a "cometary origin".

During a concert in the Portuguese city of Barcelos, the object was filmed streaking across the sky as the singer performed. Another video showed the skies of Porto, Portugal's second biggest city, turning bright for a few seconds.

Many contacted emergency services to report what happened. A spokesperson for the Spanish Emergency service 112, in Madrid, told Europa Press news agency it had received several calls.

Lisbon resident Bernardo Taborda, 31, told Reuters he was walking around the city with friends when the sky suddenly turned bright green: "It almost looked like daylight ... we all looked back and saw it."

"It felt like a movie, we all looked at each other and we were stunned," Taborda said. "It was amazing."

(Reporting by Catarina Demony and Ana Cantero; Additional reporting by Eleanor Whalley and Kinda Makieh; Editing by Giles Elgood)

By Catarina Demony and Ana Cantero