A group of opposition presidential candidates in the Democratic Republic of Congo asked supporters on Sunday to take to the streets to protest after provisional results of the disputed election are released.

Congo’s election commission is due on Sunday to release full provisional results from the Dec. 20 presidential election. The opposition has alleged widespread irregularities, which they say have enabled fraud.

“We categorically reject the sham elections… and its results,” the main opposition candidates said in a joint declaration. They demanded fresh elections be held with a new electoral body on a date to be agreed by all.

“We call on our people to take to the streets en masse after the proclamation of the electoral fraud,” it said.

The government of Congo had previously rejected calls for a rerun of the elections.

Logistical setbacks, an election day over-run, and an opaque vote-count have fuelled a dispute that threatens to further destabilise a country roughly the size of Western Europe and the world’s top producer of cobalt and other prized industrial commodities.

A tally of votes released by the national election commission, known as the CENI, in the past week shows President Felix Tshisekedi with a commanding lead over his 18 challengers, with more than 72% of around 17.8 million votes counted so far out of an as yet unspecified total.

The full provisional results from the presidential vote are scheduled to be announced by the CENI from 1300 GMT.

Since election day, some of Tshisekedi’s main challengers, including former oil executive Martin Fayulu, have been calling for a re-run of the presidential and legislative elections, accusing the CENI of allowing the vote to be tipped in the president’s favour.

The CENI and the government have dismissed these allegations and also warnings from independent observer groups that the unscheduled extension of voting and other incidents on election day and during the tabulation of votes may have compromised the credibility and legal footing of the poll.

On Thursday, the joint vote-monitoring mission of Congo’s powerful Catholic Church and its Protestant Church urged the CENI only to publish results based on correctly consolidated tallies from local polling centres.

The law requires the CENI to publish the results polling station by polling station – a bid to improve transparency and allow results to be easily double-checked to avoid the disputes that have bedevilled previous elections.

Opposition frontrunner Moise Katumbi has already ruled out mounting a legal challenge to the CENI’s results, citing the alleged lack of independence of state institutions. He has vowed to hold more protests against the election, after police forcibly broke up a banned march on Wednesday.