Update, Aug. 31, 6.03pm: Water canons have been deployed.

Some blue spray is being used to mark out protesters:

Hong Kong Police are now spraying some sort of blue stuff at protestors.
(Source: @telegram)#HongKongProtests#antiELABhk #antiELAB pic.twitter.com/5IuG3dzyRg

— Alex Hofford (@alexhofford) August 31, 2019

Original story:

Thousands of demonstrators have taken to the streets of Hong Kong defying a police ban on marches on Saturday, Aug. 31, 2019.

Hong Kong was bracing for another weekend of protests after a wave of arrests of prominent pro-democracy activists and politicians on Friday.

After the arrests of prominent pro-democracy activist Joshua Wong, organisers of a major march planned for Saturday afternoon cancelled the event.

Under heavy rain, thousands showed up anyways, following parts of the original route, and bringing traffic to a standstill.

The march is to mark the anniversary of a decision by Beijing in 2014 to limit democratic reforms in the semi-autonomous Chinese territory.

Who took part in march?

Elderly and middle-aged residents and children were in the crowd dressed in black and normal clothing.

They were, as part of the current leaderless revolution, chanting: “Fight for Hong Kong, stand with Hong Kong!”

Police warned demonstrators to “stop their illegal acts immediately” by Saturday afternoon, but to no avail.

Groups of protesters then spread out across Hong Kong island, occupying main roads.

It is Hong Kong’s 13th straight weekend of protests.

What can authorities do?

Hong Kong’s chief executive, Carrie Lam, has hinted that a draconian emergency law could be enacted.

It would give the government sweeping powers to crack down on demonstrators.

Police vans were deployed around China’s representative office where the planned march was set to end.

The perimeter of the building has been lined with a wall of water barricades.

A train station near the Chinese liaison office was shut.

Could irritate Beijing further

This last weekend of August is seen as a potential watershed for the movement.

Beijing is assumed to be anxious to stop the protests before Oct. 1, which marks 70 years since the founding of the People’s Republic, a politically important anniversary.

Earlier on Saturday, hundreds had filled a sports stadium, singing Sing Hallelujah To The Lord and holding posters featuring Lam with a bloodied eye -- both a reference to a protester who was blinded in one eye and the embattled leader continuing to take a beating from Hongkongers.

Beijing has ordered Lam not to concede to any of the protesters’ demands.

Demonstrators tactics constantly evolving

To circumvent the police bans on demonstrations, demonstrators have called for a “shopping day” in the commercial district of Causeway Bay, because the police cannot stop ordinary citizens from all showing up at one place with the intention to buy things.

The protest group the Civil Human Rights Front (CHRF), the organiser of Saturday's cancelled march, called on residents to turn on their mobile phone torches and yell slogans of the protest movement at 8.31pm local time.

Earlier in the day, an online forum called LIHKG, which protesters use to organise their movement, said it had suffered a series of denial-of-service attacks.

Background to 2014 Umbrella Movement

This Saturday, Aug. 31 marks five years since China handed down a proposal to introduce democratic elections in Hong Kong, as laid out in the basic law, the territory’s mini constitution.

However, China’s proposal allowed for popular election of Hong Kong’s leader, the chief executive, only among candidates chosen by an election committee dominated by pro-Beijing members.

The proposal kicked off two months of pro-democracy protests, known as the Umbrella Movement, in the autumn of 2014.

The demonstrations in the summer of 2019, have now lasted longer than the Umbrella Movement.

The momentum has surprised both protesters and residents.

But the likelihood of the situation ending peacefully now appears to be low.

In other news, Hong Kong is on the cusp of a recession.