Cambodia on Monday banned exiled opposition figurehead Sam Rainsy from running for office for 25 years after he urged people to spoil their ballots at this weekend’s general election.

Sixteen other senior opposition members and activists — who are in self-exile — were also removed from voting lists, banned from running for office for 20 years and fined $2,500 each, according to documents released by the National Election Committee (NEC).

Voters head to the polls Sunday, with Prime Minister Hun Sen’s Cambodian People’s Party running almost unopposed after its main challenger was barred from contesting on a technicality.

Recent law amendments, ordered by Hun Sen to counter calls for a poll boycott by opposition activists, ban anyone who does not vote in the upcoming poll from running in future elections.

It is also illegal to obstruct the voting process or call for voters to spoil ballots.

Sam Rainsy, who was also fined $5,000, was sued for “being the ringleader in instructing and inciting voters to destroy or spoil ballots”, the NEC ruling said.

Sam Rainsy and his colleagues could also face criminal charges, according to the NEC.

In the past few days, Sam Rainsy has called on Cambodian voters to void their votes when they go to polling stations on Sunday.

“It gives Cambodians a way to call for genuine elections,” he tweeted on Monday.

He has lived in France since 2015 to avoid jail on a number of convictions he says are politically motivated.

In the run-up to Sunday’s vote, Cambodian authorities have arrested several opposition members and activists from the Candlelight Party, which has been barred from running in the polls over registration technicalities.

Two party members were arrested on Friday and charged with inciting voters to spoil their ballots.

Another two activists were arrested on Monday on similar allegations, according to pro-government media outlet Fresh News.

Rights groups accuse Hun Sen, who has ruled Cambodia for nearly four decades, of using the legal system to crush opposition to his rule.

Hun Sen is campaigning for re-election but is expected to pass on the leadership to his eldest son, Hun Manet, in the future.

Scores of opposition politicians have been convicted and jailed during his time in power.

Opposition leader Kem Sokha was in March convicted of treason and sentenced to 27 years in prison over an alleged plot to topple Hun Sen’s government. He is currently serving his sentence under house arrest.

By Agence France-Presse