Yellow balloons that were released in New York to advertise the Spanish capital Madrid have been watched on YouTube by more than 3 million people, many of whom believe they could be unidentified flying objects (UFOs), the Spanish daily El Pais reported Tuesday.
Dozens of balloons were released last Wednesday to mark the centennial of Madrid's central Gran Via avenue in the framework of a tourism campaign, DPA reported.
As the balloons rose to the sky over Manhattan, they were filmed by several US television stations in programmes which YouTube users then placed on the internet.
The most popular of the videos, titled UFOs over New York, makes it clear that the flying objects are balloons, according to the daily.
Other videos, however, left the impression that the objects could be UFOs, with one television channel even consulting a NASA expert on the subject.
The balloons made their appearance shortly after a book, Challenges of Change by Stanley Fulham, predicted the arrival of UFOs over the world's main cities, El Pais pointed out.