Half of recorded UFO sightings remain unexplained, a new report released by US intelligence has reportedly found.

The Office of the Director of National Intelligence dossier is the first annual report into what are officially called Unexplained Aerial Phenomena.

Its release follows the landmark Congressional hearing in Washington in May and last year’s Pentagon report into UAPs, which studied 144 reports of UAP encounters.

The 22-page report analyses 366 cases but only about half of them could be explained, two sources close to the department told the DailyMail.com.

They include video shot by Reaper drones conducting surveillance in the Middle East that caught "orbs" flying around then "then "suddenly bolting off the screen".

Others are similar to he encounters filmed by F-18 pilots whose cameras picked up Tic-Tac type objects, said the source.

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