The teenage Christian leader of Hong Kong's pro-democracy 'Umbrella' movement, which protested against Beijing's grip on the city's electoral system, has said he does not regret his involvement after being handed a community service sentence.

Joshua Wong, 19, faced up to five years in jail for mobilising thousands of students in 2014 to demonstrate against the Chinese government's insistence on screening political candidates in Hong Kong to ensure their allegiance to the Communist party.

A court on Monday sentenced Wong and two other student leaders for their role in organising a peaceful-sit in that led to a 79-day protest.

Wong received a community service order of 80 hours, while Nathan Law will serve 120 hours, both for "unlawful assembly". Alex Chow was given a three week sentence with one year suspension for "incitement".

Wong said on Twitter that he did not regret his involvement.

Wong – who was raised in a Christian family – told Christian Today last year that his faith has strengthened his determination to fight for justice. When he was a boy, his father took him to visit poor communities in Hong Kong, and instilled in him a passion to advocate on behalf of the vulnerable.

"The Bible teaches us that we need to fight for justice, and Christians bear the responsibility to be salt and light in society," he said. "We have more obligation and a more important role in the world other than being just a normal citizen in society who wants to earn money."

All three sentences violate the young men's right "to peaceful expression and assembly", Human Rights Watch (HRW) said on Monday, urging Hong Kong to revoke the convictions.

"In sentencing these students, Hong Kong authorities' behavior increasingly resembles that of their counterparts in Beijing," said Sophie Richardson, China director at HRW.

"Leading peaceful protests is no crime, and the charges against the three should be dropped."

HRW warned that there have been an increasing number of arrests and prosecutions against protestors in Hong Kong, some under the Public Order Ordinance which has been criticised by the UN Human Rights Committee for possibly "facilitat[ing] excessive restrictions" to basic rights.

Under the law, processions with more than 30 people and assemblies with more than 50 must receive advance permission from the government.

Richardson said the prosecution of Wong, Law and Chow "should unnerve anyone who cares about the fate of basic rights in Hong Kong".

"Hong Kong's future depends on authorities devoting their energies to upholding – not reducing – civil and political rights," she added.