Former League of Social Democrats chairman Andrew To Kwan-hang was fined HK$2,000 for causing public disorder in a rowdy protest against the government budget.
Fellow member Wong Ho-ming was fined HK$1,000 for the same offense, while two other demonstrators - Ip Ho- yee and Yip Po-lam - were placed on probation for a year.
During a hearing at the Eastern Magistrates' Court yesterday, To and Wong admitted charges of assisting or taking part in an unauthorized assembly during the protest on March 6 last year.
To and Wong, along with 100 demonstrators, sat down and blocked traffic in Central after they joined thousands of others protesting against the plan by Financial Secretary John Tsang Chun- wah to offer HK$6,000 cash handouts to residents.
The atmosphere got tense after demonstrators broke through a police cordon to block part of Des Voeux Road, which brought traffic to a standstill.
In handing down the sentence, magistrate Winston Leung Wing-chung said the court was lenient on To and Wong as they are willing to be responsible for their actions and plead guilty to the charges.
Leung said that since To and Wong did not incite demonstrators and it resulted in no casualties, he did not impose a jail term.
Leung also noted that To and Wong should have considered the adverse impact of their actions on the public before staging the protest.
News reports at that time said police officers fired pepper spray on the protesters and took about 50 of them into custody.
Almost 100 protesters stormed the intersection of Des Voeux Road Central and Ice House Street, bringing traffic to a halt.
Police fired pepper spray to disperse them but to no avail. At 10pm officers started to carry protesters away to vans before taking them to police stations.