TOKYO (Reuters) - Japan was on alert on Saturday amid fears that the executions of the former leader and members of a doomsday cult behind the deadly Tokyo subway sarin gas attack in 1995 could spark acts of retaliation by supporters or newly formed groups.

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Japan hanged Shoko Asahara on Friday and six other members of the Aum Shinrikyo cult, which killed 13 people in an attack that shattered the country’s myth of public safety.

Police and the Public Security Intelligence Agency were collecting intelligence and monitoring followers of Asahara, Kyodo news agency said on Friday, citing warnings by a senior police official that Aum followers remained active.

The agency said it searched 16 facilities belonging to three groups across Japan on Friday, including those of the cult’s formal successor and a splinter organization launched by a former Aum spokesman, Kyodo reported.

The executions led domestic media to examine how Aum was able to recruit its followers - many of whom were young and highly educated - and whether its offshoots or other newly formed groups could do the same.

The Nikkei business daily said in an editorial the influence of Aum remained and that cults were still looking to recruit young people.

“From street corners, universities, and the world of the internet, cult-like groups that target young people have not disappeared,” it said.

“The conditions for young people to fall into the darkness of Aum - isolation, dissatisfaction with the state, and dissemination of extreme ideas - are actually becoming stronger.”

Others questioned the ability of cults or similar groups to recruit followers on the scale achieved by Aum, let alone reach the level of organization and equipment needed to stage major attacks.

Aum, which mixed Buddhist and Hindu meditation with apocalyptic teachings, had at least 10,000 members in Japan and overseas at its peak, including graduates of some of the country’s top universities.

Hirohito Suzuki, a professor of sociology at the Graduate School of Project Design in Tokyo, said a combination of greater surveillance of Aum’s offshoots and greater societal awareness meant it was now difficult for groups to obtain weapons or carry out military-style training.

Individuals who identify with the cult or Asahara were more likely to launch attacks, he said.

“There is a possibility that people who have sympathies with Asahara could launch acts of violence in towns, or near stations,” Suzuki said. “It’s very difficult for authorities to monitor those lone-wolf individuals.”