HONG KONG - The trial of the nine democracy campaigners accused of causing public nuisance with their involvement in the 2014 Occupy Central movement started on Monday (Nov 19) with all of them pleading not guilty.

The nine are: law professor Benny Tai, sociology professor Chan Kin Man, baptist minister Chu Yiu Ming, lawmakers Tanya Chan and Shiu Ka Chun, student leaders Tommy Cheung, Eason Chung, opposition parties' Raphael Wong and Lee Wing Tat.

The founders of the movement - Chan Kin Man, 59, Benny Tai, 54, and 74-year-old Chu Yiu Ming - have been served with three charges each, while the rest are facing between one and three charges each.

The charges, based on colonial-era law, carries a jail term of up to seven years.

The nine had allegedly urged people to occupy Hong Kong's business district in 2014 if the public was not given a fair vote for the city's leader, who is appointed by a pro-Beijing committee.

Before the hearing on Monday morning, the nine campaigners had gathered outside West Kowloon Magistrate's Courts with supporters carrying yellow umbrellas and chanting "we want universal suffrage" and "defend Hong Kong's democracy".

In its opening address before a packed courtroom, with more than 120 seats in the public gallery filled up, the prosecution accused the nine campaigners of creating public nuisance with their participation in the Umbrella Movement protests, and inciting others, including students who have since been prosecuted, to do the same.

The prosecution alleged the activities were unlawful and conducted in an unreasonable way that could have caused injuries.

The nine are also accused of urging protesters to stay put, and getting friends to provide supplies like food and drinks as well as defend various checkpoints.

The prosecution said the Occupy movement was not genuine civil disobedience, and the nine had met up several times to conspire to create public nuisance while openly voicing their intentions and plans.

The prosecution, which will call six witnesses to testify in the case and rely on videos taken by police officers as evidence, alleged that the movement resulted in protesters blocking a travelling fire engine, causing a delay in response time.

Instead of winning reform, critics said following the movement, Beijing tightened its grip on the city with pro-democracy activists prosecuted or jailed.

The hearing is expected to last about 20 days.