Congo-Brazzaville's leader has said he will hold a referendum on whether to change the constitution to allow him to stand for a controversial third term.

"I decided to give the people a direct voice," said President Denis Sassou Nguesso, 72, who has ruled for more than 30 of the past 35 years.

The proposals would allow candidates aged over 70 to run for office and scrap the two-term limit. No date was however given for the referendum, but elections are due next year.

The main opposition coalition is against the move, saying it could destabilise the country. It also complains that it will not have the same access to the media to voice concerns. It boycotted what President Sassou Nguesso called a "national dialogue" in July, when about 400 representatives of political groups, trade unions, war veterans as well as traditional and religious leaders were invited to discuss the constitutional amendments.

The forum was described as a "constitutional coup" by the president's critics.

Mr Sassou Nguesso, one of Africa's longest-serving rulers, was installed as president by the military in 1979 and lost the country's first multi-party elections in 1992.

He returned to power in 1997 after a brief but bloody civil war, in which he was backed by Angolan troops, and has since won two elections.

The issue of third terms is contentious in Africa.