Afonso Dhlakama, Mozambique's long-time opposition leader and former rebel chief, has died aged 65, according to media in the country.

Dhlakama, who headed the former rebel Mozambique National Resistance (Renamo) movement, passed away in the central town of Gorongosa, state broadcaster TVM said on Thursday.

It gave no details of how he died.

Dhlakama was ill prior to his death, the Portuguese news agency Lusa reported, citing an unnamed official in Renamo. Local media reported that he had suffered a heart attack.

President Filipe Nyusi, whose ruling Front for the Liberation of Mozambique (Frelimo) movement fought a long and bitter civil war against Renamo, said Dhlakama's death marked "a bad time" for Mozambique.

"To me is even worse because I was in a full alignment with him to solve the problems of this country," he said on TVM.

Members of Dhlakama's party have clashed with government forces since he lost a disputed election four years ago.

But he was set to run again against Nyusi in next year's elections.

Dhlakama's forces and Frelimo fought a long bush war in which around one million people are believed to have died.

It was ended in 1992 under a peace accord that gave fighters a blanket amnesty and allowed Renamo to regroup as an opposition party, paving the way for landmark elections two years later.

Dhlakama lost every major election he contested against Frelimo, though he topped the vote count in several central and two northern provinces in 2014.

Succession plan

Mozambique will hold presidential, legislative and provincial elections in October 2019, with observers saying Renamo has recently increased its public support.

Frelimo has ruled the country since independence from Portugal in 1975.

Low-level violence erupted between government troops and Renamo from 2013 to 2016, with the discovery of mass graves of recent victims fuelling fears that the country was heading back to war.

The fighting often centred on the country's main roads, with Renamo, which also holds seats in parliament. attacking government convoys and civilian vehicles, and soldiers accused of ruthlessly targeting suspected rebels.

The violence forced thousands of people to flee to government-run camps, relatives' homes or across the border to Malawi and Zimbabwe.

Renamo alleges that the Frelimo elite has enriched itself at the expense of the country, with the once-booming economy badly hit in recent years but a massive hidden debt scandal.

Zenaida Machado, Mozambique specialist at Human Watch, said Dhlakama's " death and the unknown succession plan within Renamo will bring uncertainty.

"It raises critical questions about the next Renamo leader's ability to control hundreds of armed men in the bush and negotiate a long-lasting peace deal with the government," she told AFP news agency.