Japan on alert for revenge attacks after execution of doomsday cult leader

Followers of Shoko Asahara and Aum Shinrikyo believed to still be active

Japanese police fear supporters of the doomsday cult behind the Tokyo subway sarin gas attack could carry out violent retaliation for the execution of the the group's former leader.

Shoko Asahara was hanged with six other members of the Aum Shinrikyo on Friday, more than two decades after his followers killed 12 people and injured thousands during the rush hour on 20 March 1995.

Officials continue to monitor followers of Asahara, who claimed to be a reincarnation of the Hindu god Shiva, over fears that cults are still looking to recruit young people.

A senior police officer said that Aum followers are "still active" and could increasingly view him as divine after his execution, according to the Kyodo news agency.

Aum renamed itself Aleph in 2000 and two splinter groups have been formed by high-profile former members.

Since Friday morning the Public Security Intelligence Agency have searched a total of 28 facilities used by the three groups across Japan.

"As a result of conducting inspections on the above facilities, no concrete signs or illegal incidents occurring in dangerous acts were confirmed at any facility," the agency said in a statement.

"We will continue to implement observation appropriately and rigorously and make every effort to ensure public safety. We will strive to alleviate the sense of fear and anxiety of the people."

In total the three groups are believed to have more than 1,650 followers.

A riot squad was deployed in front of the Tokyo detention house as reporters gathered outside the gates to cover the executions.

Hirohito Suzuki, a professor of sociology at the Graduate School of Project Design in Tokyo, said the surveillance of the groups meant it was not difficult for them to obtain weapons but warned of possible "lone-wolf" attacks.

“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.”

Aum Shinrikyo after a pilgrimage to the Himalayas in 1987 and changed his name shortly afterwards. Aum is a sacred Hindu symbol and Shinrikyo means "supreme truth".

It is thought that it had 10,000 followers at its peak and the group gained official status as a religious organisation in Japan just two years after it was formed.

Drawing wealthy and well educated members, Ashara told them he was telepathic and he could teach them levitation. He would charge them to drink his bathwater and blood.

Asahara was captured two months after the Tokyo attack and was convicted in 2004 of killing a total of 27 people during his six year campaign of terror.

He was sentenced to death but has remained on death row while the appeal process was exhausted.

Additional reporting by Reuters.