Comoros President Azali Assoumani has granted sweeping new powers to his son, Nour El Fath, allowing him to intervene at all stages of government decision making, after putting him in charge of coordinating government affairs last month.

Assoumani, 65, whose re-election in January was tainted by allegations of voter fraud, has been accused by opponents in the Indian Ocean nation of preparing his son to replace him when his term ends in 2029. He has not commented on the allegations.

El Fath did not immediately respond to a request for comment.

"There is no doubt that Colonel Azali Assoumani, by granting presidential and constitutional prerogatives to his son, is preparing the latter to succeed him," Franco-Comorian lawyer Saïd Larifou, a political commentator, told Reuters.

In his role, El Fath's powers will include evaluating ministers and intervening at all stages of the execution of government decisions, according to a presidential decree published on Tuesday.

The 40-year old worked as a senior economic adviser to Assoumani from 2019 before taking up the position of the secretary general of the government on July 1.

Government spokesperson Fatima Hamada said the presidential decree clarified and formalised El Fath's prerogatives as secretary general.

Comoros, a group of three islands off the coast of Mozambique, 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.