The finding was welcomed by UFO groups, despite the sceptical tone of the scientists, who hinted that natural phenomena are probably at the root of many reports.
"The fact that a number of scientists from different countries and credible backgrounds have been prepared to look seriously at the data is amazing. It wouldn't have happened 10 years ago," said Graham Birdsall, editor of UFO magazine, a British publication with a worldwide circulation of 140,000.
A nine-member panel led by a physicist from the august Stanford University in California declared yesterday that some of the thousands of UFO sightings reported over the past decades merit further study.
But Peter Sturrock, the panel's director, said: "If there is an interest in trying to get serious answers to the UFO problem, it would be sensible for scientists to focus on the physical evidence as opposed to witness testimony."
Phenomena such as "ball lightning" are believed by many scientists to be at the heart of many of the more credible sightings of UFOs. More recently, neuroscientists have found a means of recreating the sensations described by people claiming to have been abducted by aliens - such as a memory of grey visitors and a feeling of paralysis on waking up.
But the scientists added that some of the physical evidence remained unexplained and researchers might learn something new in evaluating purported UFO sightings.
The panel's report is the first independent review of UFO phenomena since 1966, when the US Air Force commissioned Colorado University to conduct a scientific study of UFOs headed by Dr Edward Condon.
Sturrock's panel examined evidence including photographs of purported UFOs, radar data and reports of soil damage near supposed UFO landing sites. Some of the reports could have been explained by rare natural phenomena such as electrical activity above thunderstorms. Other reports were produced by secret military activities, the report concluded.
The study was the brainchild of Laurance Rockefeller, Henry Diamond and Sturrock, who felt the field of UFO study "is in a very unsatisfactory state of ignorance and confusion". The panel was financed by the LSR Fund, chaired by Rockefeller.
Comprised of astronomers, physicists and experts in other scientific disciplines, the panel met last year in New York to discuss the data and in San Francisco to finalise the report.