It was a sight a Cote St. Luc doctor says he'll never forget.

Cleve Ziegler said though it sounds crazy, he spotted what appeared to be UFO above Cavendish Mall at about 1 o'clock Wednesday morning.

Ziegler said he was anxious to get home after a long night working in the OR, but saw something as he drove along Cavendish Blvd, that made him stop and exit his vehicle.

"This thing was just too compelling, too unusual. It merited that kind of reaction," he said, describing a cluster of small bright lights moving erratically across the sky.

"It seemed to come closer, go further, rotate on its axis, and move around randomly in a motion that I really can't describe. It's not analogous to anything else I'd ever seen," he said.

Ziegler, who reported the sighting to police, asked two other people nearby if they saw it too. They did.

Montreal police confirm they also received two other calls from people reporting strange sightings in the sky -- one from Cote St. Luc and another from the East End.

Police confirmed they investigated the claims, but found no evidence of abnormal movements in the night sky.

It's not the first time Montrealers have claimed to see an unidentified flying object. A video posted to YouTube in July shows something similar to what Ziegler described.

Astronomy expert Andrew Fazekas said what Ziegler saw could have been anything from the lights of a helicopter, to the twinkling of a planet, to a satellite streaking across the sky.

The night sky can be unpredictable, especially to the untrained eye, said Fazekas.

"I've personally been looking at the skies very intently as a stargazer for over 30 years, and I've never seen anything that cannot be explained by either a man-made object or a natural astronomical phenomenon," he said.

Ziegler, who has never believed in UFOs, said he is convinced that what he saw doesn't fall into any of those categories, and is now questioning what else it could be.