Police in Hong Kong discovered a stash of powerful homemade explosives as the city prepared for another major pro-democracy protest on Sunday, and counter-demonstrators rallied on Saturday.

Police said they found about 2 kilograms (4.4 pounds) of TATP and arrested a man in a raid on a commercial building late Friday night.

TATP, or tri-acetone tri-peroxide, has been used in terrorist attacks worldwide.

The finding comes as tension between pro-democracy activists, counter-demonstrators and police forces continues to escalate over the controversial “extradition bill” in Hong Kong, but a police spokesperson said no link has been established and the investigation is ongoing.

In recent weeks, millions have taken to the streets to protest against the bill, which would have allowed people in Hong Kong to face trial in mainland China.

Aftermath of protesters storming Hong Kong government HQ: In pictures Show all 15 1 /15 Aftermath of protesters storming Hong Kong government HQ: In pictures Aftermath of protesters storming Hong Kong government HQ: In pictures The lobby of the Legislative Council building in Hong Kong is seen covered in graffiti after it was stormed by protesters Getty Aftermath of protesters storming Hong Kong government HQ: In pictures Police officers stand guard at the Legislative Council building in Hong Kong after it was stormed by protesters EPA Aftermath of protesters storming Hong Kong government HQ: In pictures The colonial flag of Hong Kong hangs in the chamber of the Legislative Council after protesters stormed the building Reuters Aftermath of protesters storming Hong Kong government HQ: In pictures Police officers are seen behind cracked glass panels that were damaged by protesters trying to ram their way into the Legislative Council building EPA Aftermath of protesters storming Hong Kong government HQ: In pictures Shattered glass is seen on the outside wall of the Legislative Council of Hong Kong after protesters smashed their way in the building AP Aftermath of protesters storming Hong Kong government HQ: In pictures Riot police patrol the Legislative Council building in Hong Kong after it was stormed by protesters Getty Aftermath of protesters storming Hong Kong government HQ: In pictures Police officers inspect damage to the Legislative Council building in Hong Kong after it was stormed by protesters AFP/Getty Aftermath of protesters storming Hong Kong government HQ: In pictures A caricature of Hong Kong leader Carrie Lam is pasted on a pillar outside of the Legislative Council after protesters broke into the building Reuters Aftermath of protesters storming Hong Kong government HQ: In pictures Graffiti is seen in the chamber of the Legislative Council in Hong Kong after protesters stormed the building Getty Aftermath of protesters storming Hong Kong government HQ: In pictures Abandoned placards and litter is seen outside the Legislative Council building in Hong Kong after a protest on July 1 EPA Aftermath of protesters storming Hong Kong government HQ: In pictures A painting hung i the Legislative Council in Hong Kong is covered in graffiti after protesters stormed the building Getty Aftermath of protesters storming Hong Kong government HQ: In pictures A lift in the Legislative Council building is seen covered in graffiti and litter after protesters stormed the building Getty Aftermath of protesters storming Hong Kong government HQ: In pictures The chamber of the Legislative Council in Hong Kong after protesters stormed the building Getty Aftermath of protesters storming Hong Kong government HQ: In pictures A desk in the chamber of the Legislative Council in Hong Kong is covered in graffiti after protesters stormed the building AFP/Getty Aftermath of protesters storming Hong Kong government HQ: In pictures An area inside the Legislative Council building complex is strewn with litter and smashed glass after it was stormed by protesters Getty

Tens of thousands filled one of the city’s parks on Saturday to express support for police forces, who have been accused of using rough tactics on protesters, ahead of another pro-democracy march scheduled for Sunday.

“We are experiencing the most serious revolution after Hong Kong's handover," said former Legislative Council president, Jasper Tsang.

“We are also experiencing the most serious challenge for ‘One Country, Two Systems’,” he added, referring to the system under which Hong Kong is governed since its handover from British to Chinese rule in 1997.

Under the system, Hong Kong was allowed to retain for 50 years extensive freedoms not enjoyed in China, including an independent judiciary and the right to protest.

Protesters were mostly middle-aged older people dressed in white – in contrast with anti-extradition bill protesters, who usually wear black and don protective gear against police pepper spray and batons.

They gathered in the city’s Tamar Park, next to the Legislative Council which protesters stormed and raided on 1 July, and chanted “Support Hong Kong Police” and “Hong Kong Cheer Up”.

Some waved Chinese flags, and a giant screen behind the stage for speakers read “Safeguard Hong Kong.”

Tsol Pui, 85, president of Hong Kong Veterans’ Home, said: “Violence is intolerant. We are distressed about our home and we should absolutely stand out to support Hong Kong police, to maintain stability and rule of law in society.”

Tang King Shing, Hong Kong’s former Commissioner of Police, said: “Police, we support you. You should not have suffered from the disaster made by those thugs... We Hong Kong people come out to safeguard Hong Kong.”

Organizers said 316,000 people took part in the demonstration, while police put the turnout at 103,000.

On Sunday, pro-democracy protesters will take to the streets again.

Earlier marches have been largely peaceful, but in a recurring pattern, police have clashed with groups of mostly young protesters who use barricades to try to take over streets or refuse to disperse after the main demonstration is over.

Last weekend two initially peaceful protests degenerated into running skirmishes between baton-wielding riot police and activists, resulting in scores of injuries and more than 40 arrests.

Those fights followed larger outbreaks of violence in central Hong Kong last month, when police forced back activists with tear gas, rubber bullets and bean-bag rounds.

Activists and human rights groups have called for an independent investigation into what they describe as excessive use of force by police.

On Monday 1 July, the 22nd anniversary of the city’s handover from the UK to China, hundreds of protesters stormed the legislative council building and tore down Chinese flags.

For many Hong Kong residents, the extradition bill is the latest step in a relentless march towards mainland Chinese control of the city.

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Opponents of the extradition bill fear it would leave the people of Hong Kong at the mercy of Chinese courts, where human rights are not guaranteed, and have voiced concerns over the city’s rule of law.

Hong Kong’s embattled leader Carrie Lam has apologised for the turmoil the extradition bill has caused and declared it “dead”.

But now opponents demand the full withdrawal of the bill, the withdrawal of the word “riot” from the government’s description of demonstration and the release of those arrested.

Protesters are also advancing demands for greatest democracy and even to curb the number of mainland Chinese tourists to Hong Kong.