Britain Thursday released 35 previously classified files documenting sightings of unidentified flying objects (UFOs) by the military and members of the public dating back to the 1950s.

The files contain around 8,500 pages which mainly cover the period from 1997 to 2005 and include photographs, drawings and descriptions of flying saucer sightings, as well as letters the Ministry of Defense (MoD) sent eyewitnesses in response to their accounts.

Policemen, a soldier, a Royal Air Force (RAF) officer and members of the public report sightings of objects including a "chewy mint shaped solid craft" and aerial objects resembling a "ring," a "jellyfish" and a "silver voile spin top."

In one account a man said he believed he had been "abducted" by aliens in October 1998 after seeing an unidentified craft hover over his London home and finding he had gained an hour of time in the process.

"It was a large cigar-shaped vehicle with big projectiles on each side like wings," he told the MoD.

"It seemed to have two very bright lights at the front and a white light flashing round and round underneath... As you can imagine, I felt quite shaken."

The MoD wrote to the man informing him that the object was probably an airship, adding that the time he had gained was probably the result of the clocks being put back one hour on the night of his close encounter.

Another file released by the National Archives reveals how the RAF was inundated with calls one morning in 1967 after residents of southern England awoke to find six small beeping UFOs lying in a perfect line from the Isle of Sheppey to the Bristol Channel.

A bomb disposal unit blew up one of the UFOs, another was airlifted to the southeastern village of Aldermaston and both the army and the MoD's intelligence unit were mobilised for what was considered a real "alien invasion."

It was later discovered that engineering students at Farnborough Technical College had constructed and positioned the UFOs in a bid to raise money for charity.

"It does raise some questions about what really would happen if at any time in the future there was some kind of instant -- would we be prepared?" said David Clarke, author of "The UFO Files" and consultant to the National Archives' UFO project.

The files are available to download free of charge for one month at www.nationalarchives.gov.uk/ufos.