One-third of the police force on Hong Kong Island will be deployed today to keep rival protest groups in good order for what a police source described as the city's "most complicated security situation" in two years.
Tens of thousands of protesters from eight groups - five against Chief Executive Leung Chun-ying and three in favour - will gather in Causeway Bay, Wan Chai, Central and Western district to express different, sometimes conflicting political views.
Some protests will share the same route or be close to each other, raising fears of scuffles.
A senior police source said it was rare for so many groups with opposing goals to hold rallies on the same day and described it as "the most complicated situation" of the past two years.
Protest organisers said they would arrange for "hundreds of marshals" to help keep order.
On Sunday, two TV journalists were attacked by demonstrators at a pro-government rally in Victoria Park, raising concerns about more trouble today. But the police source said the force was "fully prepared", with up to 1,000 officers on duty, or about one-third of the officers stationed on Hong Kong Island.
"Police will not be siding with either camp," said the source, adding that police would "take a flexible approach" to roadside political stalls along march routes despite the ban announced last week.
"We do not allow the stalls because they could obstruct other protests along the same route," the source said. "We will give warnings to those who set up stalls, and the last thing we want is to arrest the stallholders."
Chief Superintendent Eddie Wong Kwok-wai said: "We want the rallies to take place peacefully but we will take action if the laws are broken."
Icarus Wong Ho-yin, a vice-convenor of the Civil Human Rights Front - organisers of an anti-Leung march from Victoria Park to the government headquarters in Admiralty - said the group would call up around 200 marshals to keep order. The organisers have notified police of a turnout of 50,000 but expect more people will join.
"We were not so worried about order before, but we were shocked to see what happened on Sunday and fear it may be repeated" today, he said.
"We will ask marshals to look out for anyone sneaking into the crowd and creating chaos. If an argument arises, we hope our marshals will move in as quickly as possible and appeal to everyone to stay apart and keep calm."
A pro-Leung rally is scheduled for 3pm to 8pm at the Tamar Park Amphitheatre, organised by the Voice of Loving Hong Kong. Anti-Leung protesters will gather nearby from 7pm.
Patrick Ko Tat-pun, convenor of the pro-Leung rally, said they would have 20 to 30 marshals to maintain order, and would film any violence.