Japan has experienced some anthrax hoaxes

Six years later, on a wet afternoon in a Tokyo suburb a long vigil continues.

Local residents with police and other government agents are keeping watch on a group once as notorious as Osama Bin Laden's al-Qaeda is today.

They are loitering under umbrellas outside the headquarters of Aum Shinrikyo.

Kasauki Faruma is a newsagent who takes turns to stand guard.

"Everyone's angry that Aum was not banned," he says. "We can't solve the problem ourselves.

"If we drive them away they'll only set up in somebody's else's neighbourhood.

"The government has to take responsibility and close it down."

Shocking signal

The Aum cult is described by the US State Department as a terrorist organisation. But after the arrest of many of its leaders, it still operates openly here in Tokyo.

They succeeded with chemical weapons, because they're relatively simple and easy to produce

Professor Keichi Sunayishi

Many believe the government has learned very little from its experience of biological and chemical terrorism.

The sarin nerve gas attack on the Tokyo subway was a shocking signal to the world that terror groups could get their hands on chemical weapons. In addition to the 12 people who died, thousand were made ill.

But such is the deadly power of sarin it could have been much worse.

The attack was the culmination of a five-year plan to develop a huge arsenal of chemical and biological weapons. Cult members at first experimented with the germs botulism and anthrax. On at least 12 occasions they sprayed the bacteria into Tokyo's streets.

But the strains of the disease were not potent enough and in frustration the cult turned to chemical weapons.

"They succeeded with chemical weapons, because they're relatively simple and easy to produce," says Professor Keichi Sunayishi who specialises in the subject at Kanagowa University.

"But biological weapons are live agents and not so easy to handle.

"The anthrax they got hold of appears to have been suitable for a vaccine only and was not potent enough. They also had trouble delivering it. "

On alert

The cult has now changed its name to Aleph and has publicly renounced violence. It has just over 1,000 members, but it once had 10 times that number, including scientists and technicians and assets of hundreds of millions of dollars.

Despite all its resources it still failed to bring about the cataclysm it planned for.

Cult founder Shoko Asahara is in jail

This is perhaps a reassuring sign, but Shoko Agawa, who has written about the group for 10 years, and survived an attempt on her own life, is not so sure.

"The group suffered from a major structural weakness," she says. "Only the leader of the cult, Shoko Asahara, knew what was going on, what they were trying to achieve.

"Followers just did what the guru told them to do. They didn't have the courage to give accurate reports of their failures, so never learned from them."

The Japanese police last week staged a mock exercise to show their preparations for biochemical attacks. But the special 10-man unit was not formed until five years after the Sarin attack. Only now is it being expanded.

It has taken the events of 11 September in the United States to remind Japan that it could still be vulnerable.