WASHINGTON: The conclusion of a classified US intelligence report on the existence of alien UFOs is . . . inconclusive, US media reported Friday.

US military and intelligence found no evidence that seemingly highly advanced unidentified flying objects sighted by military pilots were alien spacecraft, the report concludes, according to the New York Times and other media briefed on it.

But it also could not explain dozens of phenomena and incidents, some filmed by the pilots, and so could not rule out the existence of aliens.

According to the New York Times, citing unnamed senior administration officials, the report determined that most of some 120 incidents over the past 20 years had nothing to do with unknown or secret US military or government technology. Nor were they related to objects like research balloons, which some postulated were behind the reports.

But it then could not explain what, for example, US Navy pilots saw when they recorded objects travelling at seeming hypersonic speeds, spinning and mysteriously disappearing.

While speculation over alien life has long been a cottage industry for conspiracy theorists, the sheer number of what the Pentagon terms unidentified aerial phenomena (UAP) has made it a serious issue, amid worries that US adversaries like China and Russia may be using unknown, highly advanced military and surveillance technologies. The report, ordered last year, is to be submitted to Congress by the end of June by the director of national intelligence.

The main report will be unclassified and can be made public, but there will also be a classified annex, the Times said, that will remain secret.