BERLIN (Reuters) - Numerous sightings of massive fireballs in the skies over Germany this week have led to an upsurge in reports of UFOs, but scientists believe the cause could be a bizarre annual meteor blitz. According to the Web site of the U.S. National Aeronautics and Space Administration ( NASA), such fireballs have been reported elsewhere in the world and may also be due to the fact that the Earth is now orbiting through a swarm of space debris. Many people in Germany have noticed the fireballs, said Werner Walter, an amateur astronomer in Mannheim who runs a Web site on unexplained astronomical phenomena and a hotline for reports on unidentified flying objects (UFO). "The last reported sighting was yesterday at 7:30 p.m. (1830 GMT) in a corridor near the border of the Netherlands," he told Reuters in a telephone interview. "This week we have had at least 15 emails and phone calls from people reporting these fireballs," he said. "Some people said it looks like something out of a science fiction horror film." In addition to a possible meteor streak, Walter said amateur and professional astronomers were considering the possibility that the blitz was the result of a "falling satellite or UFOs." "It is possible that they are UFOs, which are after all things which we cannot explain," he said. NASA's science Web site (http://science.nasa.gov) mentions reports of recent fireball sightings in the United States, Canada, the Netherlands, North Ireland and Japan. It includes images of the fireballs, which one man likened to a spotlight. Walter described them as "super-large, coloured fireballs that shoot with the speed of lightning through the sky". However, the NASA Web site quotes meteor expert David Asher from the Armagh Observatory in Northern Ireland as saying that people "are probably seeing the Taurid meteor shower". Taurids are meteors that shoot out of the constellation Taurus, which peaks at the end of October and early November.