Official results show voters have approved changes to the constitution that will allow Republic of Congo's longtime leader to seek another term.

President Denis Sassou N'Guesso would have been barred from seeking re-election as he is already 71 and the constitution had had a 70-year-old limit.

On Tuesday, election officials said that more than 92 percent of voters had approved the constitutional changes in Sunday's referendum. The opposition, though, has raised questions about the poll, calling it a "constitutional coup."

Republic of Congo borders the enormous nation known as Congo. Sassou N'Guesso first served as president from 1979 until a 1992 election defeat. He later seized power in 1997 following a civil war and then won an election in 2002 and was re-elected in 2009.