Public security authorities are on alert amid concerns that Friday's executions of Aum Shinrikyo cult founder Shoko Asahara and former senior members could prompt groups of his supporters to become more active.

The mainstay group — renamed Aleph — and two splinter groups have continued their activities, even soliciting new young members who know less about the series of crimes committed by Aum, including the deadly 1995 sarin gas attack in the Tokyo subway system.

Aleph has about 1,450 members, while the other two groups — Hikari no Wa (Circle of Rainbow Light) and another called Yamadara no Shudan — have some 150 and 50 members, respectively. The three are all being watched by security authorities.

In recent years, Aleph has made clear its devotion to Asahara, whose real name was Chizuo Matsumoto, and obstructed inspections of its facilities by the authorities, according to the Public Security Intelligence Agency.

Aleph had assets of more than ¥1 billion as of October last year, funded mainly by fees collected from participants in its "intensive seminars" and donations by followers, the agency said.

The group recruits about 100 new members every year, especially young people, while at the same time claiming the sarin gas attack was a conspiracy against Aum, according to the agency.

Around 50 members split from Aleph in 2013 over a disagreement about who should succeed Asahara as leader. The agency believes this group is also under the influence of Asahara's practices.

Hikari no Wa, established in 2007 by former senior Aum member Fumihiro Joyu, has underscored its break with Asahara.

"While denying relations (with Asahara), they also preach absolute devotion to his doctrine," an agency official said.