Comoros President Azali Assoumani has for the first time said publicly he intends to hand power to his son Nour El Fath when he leaves office in 2029, confirming critics' accusations that he has long been grooming his son to take over.

Assoumani, whose re-election a year ago was tainted by allegations of voter fraud, put El Fath in charge of coordinating government affairs and granted him sweeping powers over the cabinet.

Referring to when the time comes for him to leave power, Assoumani said on Thursday in a speech to supporters on the island of Moheli: "I will place my son to replace me as head of the state and the party."

El Fath did not immediately respond to a Reuters request for comment but has previously said Comoros, a group of three islands in the Indian Ocean off East Africa, is not a monarchy.

Assoumani's ruling party decisively won parliamentary elections this month, although opposition parties either boycotted the vote or rejected the results, claiming fraud.

"With this statement, he has only made official what we already knew," said Abdallah Mohamed Daoudou, a spokesperson for the opposition coalition.

"But Azali is deluding himself, the Comorian people and politicians will not accept the installation of a dynastic power or a monarchy in the Comoros," Daoudou told Reuters.

Comoros has a population of about 800 000. It has witnessed around 20 coups or attempted coups since winning independence from France in 1975.

Assoumani first came to power in 1999 through a coup and has won four elections since 2002.

Constitutional reforms in 2018 extended a requirement that the presidency rotate among the three main islands from every five years to 10.

El Fath would therefore not be eligible to replace his father at the end of the presidential term in 2029 unless the constitution were changed again.