An unclassified video taken by Navy pilots that have circulated for years showing interactions with "unidentified aerial phenomena". [AFP]

UFO sightings should not be dismissed out of hand because they could in fact be surveillance drones or weapons, say Japanese lawmakers who launched a group on Thursday to probe the matter.

The non-partisan group, which counts former defence ministers among its 80-plus members, will urge Japan to ramp up abilities to detect and analyse unidentified anomalous phenomena (UAP), more commonly known as UFOs.

Although the phenomenon is often associated with little green men in the popular imagination, it has become a hot political topic in the United States.

Washington said last year it was examining 510 UFO reports - more than triple the number in its 2021 file - and NASA in September said it wants to shift the conversation "from sensationalism to science".

The Japanese parliamentarians hope to bring the domestic perception of UAP in line with its ally's following several scares related to suspected surveillance operations.

"It is extremely irresponsible of us to be resigned to the fact that something is unknowable, and to keep turning a blind eye to the unidentified," group member and former defence minister Yasukazu Hamada said before the launch.

In an embarrassment for Japan's defence ministry, unauthorised footage of a docked helicopter destroyer recently spread on Chinese social media after an apparent drone intrusion into a military facility.

And last year the ministry said it "strongly presumes" that flying objects sighted in Japanese skies in recent years were surveillance balloons sent by China.

In Japan, UFOs have long been seen as "an occult matter that has nothing to do with politics", opposition lawmaker Yoshiharu Asakawa, a pivotal member of the group, has said.

But if they turn out to be "cutting-edge secret weapons or spying drones in disguise, they can pose a significant threat to our nation's security".

 UFO 'hotspot' 

The US Defence Department in 2022 established the All-Domain Anomaly Resolution Office (AARO) to investigate UAP.

An AARO report last year designated the region stretching from western Japan to China as a "hotspot" for UAP sightings, based on trends between 1996 and 2023.

It later concluded in a congressionally ordered 60-page review that there was no evidence of alien technology, or attempts by the US government to hide it from the public.

The Japanese lawmakers will push for the country to create an equivalent to the Pentagon's AARO and to further boost intelligence cooperation with the United States.

Christopher Mellon, a UAP expert and former US intelligence official, hailed the group's launch as "remarkable".

From drones to hypersonic vehicles, the war in Ukraine has shown that "unmanned weapons and artificial intelligence are creating very serious new challenges", Mellon told the Japanese MPs in an online speech.

In December, one US Air Force base was subjected to a weeks-long, mysterious intrusion by drones, but "we still don't know where they were coming from", he said.

A "UAP effort contributes to our understanding of these kinds of issues".