HONG KONG — A demonstration in Hong Kong on Sunday against the city’s embattled government focused on protesters’ demand for an independent investigation into what they said was police brutality in earlier street clashes.
The conduct of Hong Kong’s police force has come into sharp focus in recent weeks as some of the city’s largest-ever demonstrations have thrown it into the worst political crisis since China reclaimed sovereignty from Britain in 1997. The protesters accuse the police force — which has long been known in the region as “Asia’s finest” — of using excessively violent tactics to suppress their gatherings.
It was the latest sign of growing antagonism between the largely peaceful protest movement and the front-line officers tasked with patrolling it. The police said that officers on Friday had raided an industrial building and seized about two pounds of powerful explosives, 10 gasoline bombs and nitric acid as well as bullets, slingshots, knives and metal rods. Three men in their 20s have been arrested in connection with the case.
Superintendent Alick Bryce McWhirter described the site as a “homemade laboratory” of triacetone triperoxide, a highly unstable explosive also known as TATP.
“Without doubt, this is the largest seizure we have come across in Hong Kong,” he added.
The police said they were investigating whether the explosives were related to the Sunday protest but did not yet have adequate evidence to make conclusions.
Bonnie Leung of the Civil Human Rights Front, which has helped organize the recent protests, said there was no evidence that the explosives were intended for use at the march on Sunday or any others. She said the group would keep a close eye on the crowd on Sunday and that public safety was its first priority.
On Sunday afternoon, an overwhelmingly young crowd of protesters dressed mostly in black T-shirts set off from Victoria Park in the Causeway Bay area of downtown Hong Kong. They carried signs saying “No extradition to China,” “Stop police brutality” and “Condemn police for firing on protesters!”
The mass demonstrations began in early June in response to unpopular legislation, now suspended, that would have allowed extraditions to mainland China, where the courts are controlled by the ruling Communist Party. Protesters later expanded their demands to include universal suffrage, amnesty for protesters arrested at earlier clashes and an independent inquiry into police violence.
Supporters of the push for an independent inquiry include members of the city’s pro-democracy legislative minority, the Hong Kong Bar Association and the European Parliament, which issued a statement on Thursday that called for an “independent and impartial investigation into the use of force by the Hong Kong police against the crowds.”
An open letter signed by a few hundred people who said they were relatives of police officers has also called for an independent inquiry.
“Desist from deploying police officers as human shields between the government and the general public,” the letter said, adding that the government should instead listen to protesters’ demands. The letter said police leaders had issued unreasonable commands that endangered the safety of front-line officers.
But advisers to the territory’s embattled chief executive, Carrie Lam, say her administration does not intend to make further concessions to the protesters. That stance suggests the government is confident it can weather further protests despite signs that the unrest could damage the local economy and the risk that more protests could result in injuries or deaths among demonstrators or police officers.
Police officials say that they have largely acted with restraint and only used force when attacked by protesters. They accused some of the protesters of rioting during recent demonstrations, including one in which a small group of protesters forcefully stormed the Hong Kong legislature and spray-painted political slogans.
The police and a watchdog that monitors complaints against them have said they plan to investigate the tactics used against protesters at a June 12 demonstration that turned violent. Many people in Hong Kong, a city of about seven million, believe that the police response that day — which included firing tear gas, rubber bullets and beanbag rounds — was excessive.
But the protesters and their supporters argue that the watchdog is not independent and will not conduct a fair investigation. They also note that the Hong Kong government has commissioned past inquiries over civil unrest.
The protest on Sunday came a week after a rally urging Mrs. Lam to resign and fully withdraw the extradition bill devolved into a frenzied brawl between a small group of protesters and police officers in riot gear inside a luxury shopping mall.
The protesters have also turned their anger at mainland Chinese who visit Hong Kong to shop or to buy medicine, powdered baby formula and other goods for resale across the border. Last weekend, a demonstration in a Hong Kong border town against so-called parallel traders ended in clashes with the police.
Afterward, the Junior Police Officers’ Association, a police union, issued a statement calling on the police department to safeguard the personal safety and “emotional well-being” of officers in the field.
“Unless the management level has the confidence that their tactics and equipment can ensure the safety of officers in action, they should not appoint officers to complete missions that could cause injuries or to go to dangerous areas,” the union said.
That statement came days after Mrs. Lam condemned last weekend’s street clashes and thanked the city’s police officers for “safeguarding Hong Kong’s safety at the front lines.”
“They fulfilled their duties responsibly and were very professional and restrained, but they were intentionally attacked by people who I really think we can describe as rioters,” she said, speaking on Monday at a hospital where she was visiting several officers who were injured in the clashes.
Demonstrations in support of the police have also been organized by pro-establishment groups, including one on Saturday that organizers said drew more than 300,000 people. The police put attendance at just over 100,000.