PHNOM PENH (Reuters) - Five former members of Cambodia’s outlawed opposition party were found guilty and fined $2,500 each on Thursday for calling for a boycott of Sunday’s general election.

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The main opposition Cambodia National Rescue Party (CNRP) was dissolved last year and 118 members were banned from politics for five years, part of a wide-ranging crackdown by Prime Minister Hun Sen who is looking to extend 33 years in power.

Hun Sen’s ruling Cambodian People’s Party (CPP) lodged a complaint against 30 former CNRP members in Battambang province after they posted pictures of themselves raising their index fingers on Facebook in what authorities said was an appeal to Cambodians to abstain from voting.

The CPP also complained about the sharing of messages by the former CNRP leader Sam Rainsy, who lives in exile in France.

Sam Rainsy launched a Clean Finger boycott campaign earlier this year. It refers to the ink used to stain the fingers of citizens who have voted.

“Their actions caused confusion among the population,” Hang Puthea, spokesman for the National Election Committee (NEC), told Reuters, referring to the five found guilty.

Authorities have said calls to boycott the vote are illegal, but rights groups argue the advocacy is not against the law as Cambodia has a voluntary voting system and the right to free speech in its constitution.

Hang Puthea said that Chea Chiv, a former head of the CNRP in Battambang and one of the five people fined, was banned from politics by the Supreme Court when it dissolved the party last year and could face further punishment.

Another CNRP leader, Kem Sokha, was jailed in September on treason charges which his supporters say were politically motivated. He is currently in pre-trial detention near Cambodia’s border with Vietnam.

Chea Chiv said he was worried about being arrested.

“This is the most unfair decision,” Chea Chiv told Reuters. “Laws are being interpreted in ways that benefit (the ruling party).”