(AFP) - Opposition groups in Comoros on Wednesday dismissed the results of a referendum that allowed President Azali Assoumani to run for another term as a "farce" after they boycotted the controversial vote.

Voters in the impoverished Indian Ocean archipelago on Monday overwhelmingly backed the constitutional reforms, with the election commission putting support for the move at 92.7 percent with 64 percent turnout.

"It's a farce," said Ali Mhadji, a member of an opposition grouping of parties. "We reject these results, they are false."

Under the constitution adopted in 2001, power rotated every five years between Comoros' three main islands as a means of balancing politics in the coup-prone country.

Following Monday's vote, that arrangement will be dropped and replaced by a president who will be elected for a five-year tenure, renewable for one term.

Assoumani will also gain the power to scrap the country's three vice-presidencies which was another balancing measure of the previous constitution.

Three other opposition parties on Wednesday also criticised "the false results in this so-called referendum", congratulating Comorans for their "dignified refusal to go to the polls."

The group tasked with monitoring the vote, the Eastern African Standby Force (EASF), said it had to cancel a press conference scheduled for Wednesday, without providing a reason.

The mission said Tuesday it had observed some irregularities during the vote, including a "sudden flood" of ballot papers at one polling station.

An EASF member said party representatives weren't allowed to sign official documents in any polling station, which "casts doubt over the credibility of the electoral process."

Assoumani is now expected to stage early elections next year to extend his time in office.

The Comoros -- a group of three islands between Mozambique and Madagascar and one of the world's poorest countries -- has endured repeated coups and political turmoil since independence from France in 1975.

Assoumani, a 59-year-old former colonel, was president between 1999 and 2002, coming to power after ousting acting president Tadjidine Ben Said Massonde in a military coup.

He won the country's first multi-party elections in 2002, stepping down in 2006 to hand over power democratically to Ahmed Abdallah Sambi.

In May 2016, he returned again as president after an election marred by violence and allegations of voting irregularities.

In April this year, Assoumani suspended the Constitutional Court saying it was incompetent.

© Agence France-Presse