Algeria's President Abdelaziz Bouteflika said on Sunday he would seek a fifth term in a presidential election set for April 18, the state news agency APS reported on Sunday, putting an end to months of uncertainty caused by his poor health.

Bouteflika, 81, who has been in office since 1999 but has been seen in public only rarely since suffering a stroke in 2013 that confined him to a wheelchair, is likely to win a fifth term as the Algerian opposition remains weak and fragmented.

APS said Bouteflika wanted to amend the constitution if re-elected. It did not say which specific amendments he would seek but a source familiar with the matter said he would likely propose the creation of new post of vice-president to help him govern the large, energy-rich north African nation.

Among names cited by Algerian media as a possible future vice-president are veteran former United Nations diplomat Lakhdar Brahimi and Prime Minister Ahmed Ouyahia.

Bouteflika's announcement came a day after the ruling FLN party picked him as its official presidential candidate. Several political parties, trade unions and business organisations have already said they would support his re-election bid.

His re-election would provide short-term stability for the FLN, the army and business tycoons, and postpone a potentially difficult succession.

Algeria is a key gas supplier to Europe and an ally of the United States in the fight against Islamist militants in the Sahel region of North Africa.

Bouteflika remains popular with many Algerians, who credit him with ending the country's long civil war by offering an amnesty to former Islamist fighters.