Kolkata: In the first such incident recorded in Kolkata, an unidentified flying object was spotted in the city's skies early Monday morning.

The fireball, that moved very rapidly and even seemed to change its shape and size, was photographed by a resident of Kalikapur in east Kolkata. Scientists couldn't identify the object though some believe it could be a meteor blazing a trail through the morning sky.

The object, as shown on a TV channel, seemed to alter its shape from a round object to a triangle and then turned into a straight line. It emitted a bright light that formed a circle - almost a halo - and also radiated a range of colours.

The strange object was spotted between 3.30 am and 6.30 am by a senior executive of a private company, who filmed it on his handycam and showed it to the MP Birla Planetarium director D P Duari.

Many others spotted the strange object streaking across the eastern sky and hundreds gathered along EM Bypass to catch a glimpse of the "UFO". Many claimed to have seen the UFO, triggering a frenzy.

The Birla Planetarium director said the flying object, seen "at 30 degrees on the eastern horizon" was "interesting and strange".

"The viewer first thought it was a plane but gradually its brightness increased and it went up and vanished around 6.30 am," Duari said. "No natural phenomenon is likely to last for such a long duration and it is not a meteor either. It is an extremely interesting and strange object," he added.

Scientists were also puzzled by the phenomenon. They claimed it was too early to hazard a guess on what the object could be.

"A cosmic body cannot change its appearance the way this one seemed to do. But an expert needs to observe it for a longer period of time to be able to comment on it. It is very strange and intriguing. Sadly, TV pictures are not enough to make a conclusion," said Kamalesh Kar, astro-particle physicist at the Saha Institute of Nuclear Physics.