By WILL STEWART

Vapour trail is too haphazard in shape to have been made by an aircraft...

A UFO, meteor shower… or a very drunk pilot? Mystery over the bizarre trail left in evening sky over Siberia.

Experts say the bizarre pattern could have been caused by a rocket launch, but some locals are putting the cloud down to extraterrestrial activity.

Twisting and seemingly metamorphosing with every passing second, it cast a ghostly spectre against the clear dawn sky.

For a while it was unclear what had caused the vapour trail over the southern Altai region, but it was too haphazard in shape to have been made by an aircraft.

The Siberian Times reported that with little else to go on, many speculated about the possibility of UFOs.

No official confirmation has been given by the authorities, but the strange artistic pretzel-like shape is likely to have been caused by a rocket launch minutes earlier.

Experts say the patterns are consistent with the second stage of disengagement as used parts of the rocket fall back to earth.

THIS mysterious Siberian cloud sparks UFO debate.

The Siberian Altai region is close to where a Proton-M rocket blasted off from its launch site across the border in Kazakhstan, and space debris does regularly land there.

It was launched from the Baikonur Cosmodrone at 6.16am on December 15, carrying a Yamal-401 satellite.

A number of residents in the city of Barnaul, on the banks of the River Ob, caputred photos and videos of the subsequent glowing patterns.

Extremely cold weather is required to create such clouds, with vapour from the hot falling debris meeting the freezing air.

Natalia Pavlova, the head of the Barnaul planetarium, said the patterns could have been caused by the rocket launch, but stressed falling meteors was another explanation. However, there were no reports of meteors.

Residents in Russia are becoming used to seeing mysterious lights in the sky.

Last month an unexplained explosion was witnessed above Yekaterinburg, the country's fourth largest city.

Meteorites, missiles, a plane crash, and even extraterrestrial activity were among the many theories put forward to explain the incident on November 14.

But as more videos emerged of similar flashes in the sky, attention was focused on an old chemical plant that processes explosives next door to a military unit.