It was only when the riot police charged that it became clear that dozens of people in the demonstration were plainclothes police officers.
I saw two men who had been standing beside me in the crowd take fluorescent yellow garters from their pockets and roll them up their sleeves as the riot police advanced. Then they pounced on the protester to whom I had been talking and ran him up the road, one with an arm round his neck, the other pulling at his belt.
The undercover men identified by the yellow armbands in this fashion yesterday arrested scores of supporters of the jailed former deputy prime minister of Malaysia, Mr Anwar Ibrahim, as Malaysia's political crisis entered a new and more confrontational phase.
For two hours last night after breaking up the illegal rally, riot police roamed the streets of the capital, Kuala Lumpur. They were directed down side roads and into underground train stations by plain-clothes men with mobile telephones acting as spotters.
The unprecedented defiance of a ban on demonstrations by the government of the Prime Minister, Dr Mahathir Mohamad, began in the centre of the Malaysian capital quietly enough.
A few dozen people gathered silently in late afternoon at a road junction at a corner of Merdeka Square, a grassy rectangle fronted on one side by Victorian and Moorish architecture and on the other by the Tudor-style Royal Senagal Club.
The ban was specifically imposed in the historic square, a former colonial cricket ground where Malaysia declared independence on August 31st, 1957, to avoid a repetition of a huge rally there last week in support of Mr Anwar, who was jailed for alleged sex crimes a week ago. The grass was fenced off with crush barriers, and the only person allowed inside yesterday was a mechanic dismantling with a blow torch a giant orangutan erected for the recent Commonwealth Games.
The crowd grew steadily and by 6.15 p.m. had grown to about 2,000. Hundreds suddenly began crying "Reformasi" (Reforms) and "Allah is Great" and waving their fists in the air. Two crude banners were produced with the messages, "Free Anwar" and "Mahathir Resign". People spilled across the busy avenue on the edge of the square, blocking traffic, with a couple of terrified children staring out the windows of the last car to get through.
Inevitably the riot police appeared in the distance. They advanced in three lines towards the demonstrators, beating their perspex shields with long truncheons, totally ignored by the mechanic who by this time had cut down the head of the orangutan, which lay grinning on the grass.
The riot police were followed by a large red Mercedes truck with a platform on top on which a police commander surveyed the scene and gave orders by ringing a large brass ship's bell.
When it was rung the riot police stopped. When it sounded again, the resumed their march. At a third bell, they charged. The crowd fled along a back road by the Sungal Kelang river, but scores were arrested by the plainclothes police and flung down on to the ground by the river wall.
Some who dropped to the mud 15 feet below were followed by the men with yellow garters and rounded up. Several people, some middle-aged, were kicked and beaten with batons by the riot police, but in the mayhem I did not see a single blow struck or an object thrown by a protester. The resistance was completely passive. Even those arrested did not try to struggle free.
The now-daily dramatic events in the streets of Kuala Lumpur reflect the anger of Anwar supporters at his imprisonment, which many regard as part of a political struggle.
In this Dr Mahathir, Prime Minister for the last 17 years and one of Asia's last old-style paternalistic rulers, has so far prevailed, thanks to the use of the Internal Security Act and almost totally controlled media. But diplomats in Kuala Lumpur said yesterday that Malaysia was entering uncharted waters and that the small pro-Anwar movement, with its Islamic overtones, has gained an unexpected momentum.
On Sunday evening a new 18-member coalition of Malaysian opposition and human rights groups was formed at a rally on the outskirts of Kuala Lumpur. The rally, attended by more than 10,000 people, resolved to campaign against growing authoritarianism and agitate for the release of Mr Anwar.
The Coalition for People's Democracy includes the main Islamic Opposition party, Pas, and the Chinese-dominated Democratic Action Party (DAP).
In a declaration the coalition said Malaysia was facing a political, economic and social crisis. "The police, instead of upholding the rule of law, have resorted to the Internal Security Act to arbitrarily arrest and detain people without trial and have used needless force and brutality in the process," it said, referring to the arrest of 13 prominent Anwar supporters.
Pamphlets in circulation yesterday claimed that Mr Anwar has been physically and mentally abused in custody. In a taped video message made a week ago for CNBC, Mr Anwar said sexual misconduct and other allegations against him were part of a conspiracy orchestrated by Dr Mahathir to stop him exposing cronyism and corruption.
"He wants to use the remaining time he has to strengthen the interests of his family, his cronies," he said. Dr Mahathir claimed that Mr Anwar was using public unrest to stop his trial from going ahead.
The main pro-government newspaper, the New Straits Times, yesterday hit back at Mr Anwar with a classic example of what one demonstrator described as "the pot calling the kettle black". Its main story, under the headline "Anwar's kin, friends, allies given big projects" claimed the former deputy prime minister was guilty of the same type of cronyism of which he accuses Dr Mahathir.
AFP adds from Jakarta: A prominent critic of the former Indonesian president Suharto yesterday urged the government of Mr B.J. Habibie to ask friendly foreign states to freeze all Suharto-linked assets in their countries. Mr Habibie, a Suharto protege, was handed the presidency by Suharto when the veteran leader stepped down on May 21st after 32 years in power.
Mr George Aditjondro on Sunday returned to a hero's welcome after spending the past three years in Australia, where he had fled after being put on the police wanted list for slandering Suharto.
A teacher of the sociology of corruption at Australia's Newcastle University, Mr Aditjondro is well known in Jakarta for his research, disseminated on the Internet, into the wealth of both Suharto and Habibie.