TOKYO (AFP) - On a sunny Tokyo morning in March 1995, passengers crammed onto the world's busiest subway for their normal uncomfortable rush-hour commute, unaware that a few minutes later their home city would resemble a war zone.
First came the smell, a strong and pungent chemical odour similar to paint thinner that was in fact sarin, a Nazi-developed poison so toxic that a single droplet can kill.
The sarin had been released in liquid form on five subway carriages at different points of the network, a coordinated attack by the Aum Shinrikyo cult that would kill 13 and injure thousands more.
Sakae Ito was squashed into a train on the crowded Hibiya line when he noticed the air was thick and people around him were coughing uncontrollably.
"Liquid was spread on the floor in the middle of the carriage, people were convulsing in their seats. One man was leaning against a pole, his shirt open, bodily fluids leaking out," Ito recalled.
Another commuter described the horrific effects of the sarin in a crowded space.
"I felt like I was suffocating. I coughed a lot and started shivering. The person sitting next to me collapsed and then the emergency alarms started ringing."
Passengers were keeling over, gasping for air and foaming at the mouth, with blood streaming from their noses and their eyes burning.
Police were first alerted just after 8am local time on March 20 and panic soon set in, subway workers screaming at people to evacuate as passengers convulsed on carriage floors.
Good Samaritan commuters who tried to drag victims out of the trains soon collapsed themselves, as others scrambled over bodies lying on the floor to get to fresh air.
"I saw a man lying there, bubbles coming out of his mouth. His nose was bleeding," one dazed commuter said.
Other witnesses recall seeing pieces of wet newspaper on the subway carriage, soaked in the Sarin after the attackers had stabbed pouches containing the liquid with sharpened umbrellas.
Above ground, there was pandemonium as passengers holding makeshift masks to their noses streamed from the subways stations, often vomiting and with hacking coughs.
The Japanese Self-Defence Force was called in and descended into the depths in hazmat suits and gas masks to assist the injured and deal with the poison.
Images from the time show soldiers sprinting up escalators and stairs, carrying unconscious victims slumped on their backs.
Hundreds of ambulances screamed through the streets and helicopters landed on busy roads to evacuate the injured to some 90 hospitals.
Passers-by and medics administered life-saving heart massages on pavements as others stood by, their eyes streaming with tears, either from grief or the effects of the toxin.
Others lay on the ground shaking violently but there were not enough people to attend to them immediately.
At Tsukiji station, home of the world-famous fish market, St Lukes international hospital was like a "field hospital", said Ito.
With the ambulance system overloaded, victims arrived in taxis and were pulled out and rushed on stretchers into overflowing hospital corridors that had become impromptu emergency treatment rooms.
"Nurses were running around all over the hospital," recalled Mifumi Inoue, a 55-year-old worker at the hospital.
Japan is used to natural disasters like earthquakes but in the low-crime society the news of the attack spread panic nationwide.
In the western city of Osaka, riot police were posted to several major stations and many parts of the hyper-efficient Tokyo subway system were shut down.
'MOVING GAS CHAMBER'
On a street corner near Tsukiji station, passengers thirsty for news crowded around a special edition of the Asahi Shimbun newspaper pinned up against a wall.
"The Moving Gas Chamber", headlined the evening edition of the Yomiuri Shimbun, the world's most-read newspaper.
Japan was still reeling from a devastating earthquake two months earlier in Kobe that left more than 5,000 dead.
But many said the fury of Mother Nature was preferable to the man-made attack, which left a deep psychological scar on the nation.
"We can accept earthquakes as something outside our control. We can also prepare for earthquakes," one commuter said at the time.
"But we can never prepare for something like this."