Three leading Hong Kong democracy campaigners behind the 2014 pro-democracy “umbrella movement” have pleaded not guilty to public nuisance charges.

Sociology professor Chan Kin-man, law professor Benny Tai, and Christian minister Chu Yiu-ming – founded the Occupy Central movement in 2013 and are among nine figures to face trial on Monday on criminal charges that could send some of the city’s best known activists to prison for seven years.

The justice department has prosecuted leading activists from the 2014 protests, in which huge crowds turned out to call for political reform, with some barred from standing for office and others removed from the legislature.

Most of those prosecuted have been young campaigners but now it is the turn of the older generation who originally came up with the idea of taking to the streets to demand a fairer system.

The campaigners called for the occupation of Hong Kong’s business district if the public was not given a fair vote for the city’s leader, who is appointed by a pro-Beijing committee. They urged people to join what became known as the Umbrella Movement as protesters used umbrellas to shield themselves from pepper spray.

Hong Kong bans pro-independence party as China tightens grip Read more

The campaign was overtaken by a student movement that took off in September 2014.

The three men are among nine pro-democracy defendants facing public nuisance charges for their participation in the protests, which ultimately failed to win political reform, despite bringing parts of the city to a standstill for more than two months. The defendants accept that they encouraged citizens to occupy parts of the city-state but argue that the charges are unconstitutional.

On Monday, as the trial was due to begin, more than 100 protesters rallied outside the court waving yellow umbrellas, a symbol of the pro-democracy movement, and chanting “I want universal suffrage”. Another protester held an umbrella with the words: “Power to the People.”

Facebook Twitter Pinterest Supporters of Occupy Central pro-democracy movement gather outside a court in Hong Kong

Photograph: Bobby Yip/Reuters

Campaigners say that the case raises the question of whether Hong Kong’s 50-year governing agreement with China, due to expire in 2047, still stands. The one-country, two-systems arrangement negotiated by Margaret Thatcher promised free elections and a democratic Hong Kong. Twenty-one years since the city was handed to China by the UK, there is less autonomy and weaker civil rights.

Chan has spent years negotiating for democratic changes to Hong Kong’s election system. He said: “The reason we had this protest is that China did not honour a promise to Hong Kong to let it have democracy.

“We are just an example, showing how the rise of an undemocratic China can be threatening to the rest of the world.”

Hong Kong’s quest for electoral autonomy coincided with a drive for stability by the Chinese president, Xi Jinping. He has worked to quell restive regions, most notably in Xinjiang, where up to 1 million Uighur Muslims are imprisoned in detention camps.

Hong Kong is different by design. It’s a place within China but not completely of China, with open courts, independent news outlets and many political parties.

Since the Umbrella Movement took off, the government has stifled protest and punished democracy activists, according to human rights agencies.

More than 200 people face prosecutions, including many who were sentenced to prison. Judges ejected six politicians from office, who were accused of deliberatly ignoring their official oaths. Several people were barred from seeking office because the government claimed that their political stances violated the constitution.

One young politician who joined a street brawl with police was sent to prison for six years. The tiny Hong Kong National party, an independence movement, was banned this summer. It was the first time a ban had been issued under national security law since the city’s handover. Soon afterwards, the city denied a work visa to Financial Times journalist Victor Mallet, who hosted the party’s convener at the Foreign Correspondents’ Club. Recently, he was barred from returning to the city.

“There is a snowball effect taking place here,” said Joshua Rosenzweig, the East Asian research director with Amnesty International, who is based in Hong Kong. “Those concerns about erosion of speech is what agitates young people in particular … Things are potentially more and more risky for people to speak their minds.”

Earlier this month, the UN’s Universal Periodic Review for China, a project that monitors the nation’s human rights record, recommended for the first time that China and Hong Kong strengthen civil liberties in the territory.

The Hong Kong delegate, Matthew Cheung, disagreed sharply with the conclusions. “Any concerns that Hong Kong’s freedoms of speech and freedom of the press is under threat are totally groundless,” he said.

Some of the defendants see the trial as a chance to reignite the city’s best public spirit traditions. Speeches made by defendants to urge people to join the occupation might encourage them to question if their constitution still protects their rights to share their views, said Tai, who first proposed the sit-in in 2013.

“The thing that we want to achieve with the trial is a continuation of our civil disobedience movement,” Tai said. “We need to demonstrate [this], especially to those who have not given up hope for democracy in Hong Kong.

“We can continue to strive for democracy in Hong Kong,” he added. “That may encourage or at least force people to continue their struggle, even though they may feel powerless or frustrated at this moment.”

Agence France-Presse contributed to this report