Mozambicans voted on Tuesday in an election that will test a fragile two-month-old peace deal between the ruling Frelimo party and its old civil war foe turned opposition rival Renamo.

The presidential, legislative and provincial polls are widely expected to extend Frelimo's decades-long rule over a southern African nation that is set to become one of the world's main gas exporters.

But Renamo is hoping to use electoral changes agreed in the peace pact to win control of its traditional heartlands in central and northern provinces for the first time since the civil war ended in a truce in 1992.

A failure to make those gains could cause unrest and undermine the opposition's incentive for sticking to the deal, rights groups and analysts have said.

"Mozambique has chosen peace," President Filipe Nyusi said after casting his ballot at a school in the capital Maputo. He praised Mozambicans for deciding their destiny in elections.

Carlos Alberto, a 22-year-old student waiting to vote at the same secondary school said he wanted to see parliament hold the executive to account and push through promised reforms in education, work, housing and other areas.

"We vote and then nothing happens," he said of his country, which has only known one party in power since its hard-fought independence from Portugal in 1975. Like Alberto, most of the 13 million registered voters were born after that date.

"We need to make some changes," he said.

A corruption scandal over government borrowing has hit the economy and damaged Nyusi's popularity.

A low-level Islamist insurgency in the north, on the doorstep of billion-dollar gas projects being developed by oil majors including Exxon and Total, has also taken the shine off Nyusi's presidency and threatens security longer term.

Human Rights Watch decried the closure of ten polling stations owing to insecurity in the area of northern Mozambique where the insurgency has a foothold.

FRAGILE TRUCE

Outside of Mozambique's remote north, the main security risk comes from a disgruntled opposition.

Renamo fought Frelimo for 16 years from 1977 to 1992 in a Cold War conflict that killed about a million people. It ended in a truce but sporadic violence has flared in the years since - including after Renamo challenged election results in 2014.

Under the peace deal signed in August this year, provincial governors will now be picked by the main party in each province, rather than the government in Maputo - an opportunity for Renamo to gain long-thwarted representation.

But factionalism in Renamo and the fading popularity of its leader, Ossufo Momade, could yet make winning the number of provinces it wants a tall order.

Polls were due to close at 6 p.m. (1600 GMT). Law allows 15 days for results to be announced, though they may come sooner.

Should Renamo come back empty handed, that could trigger further violence, Zenaida Machado, a researcher at Human Rights Watch, has said.

The run-up to the vote was marked by sporadic violence, including the killing of an election observer and attacks from a breakaway group of Renamo fighters that killed one person. Both opposition parties - Renamo and younger challenger the MDM - have already made allegations of vote rigging.

A crowd that welcomed Nyusi at his final campaign rally in Maputo on Saturday cheered when he promised peace would last.

That may not be enough for some voters.

"Since I was born Frelimo has been in power. I can't say they haven't done anything... but there's a lot of wrong," said Katio Arsenio, 23, a security guard.

"Better to give my vote to those who have never governed, to see what they have for us."

He was voting in an area of Maputo where the race is likely to be close. By midday, people were still queuing outside polling stations there instead of taking shelter from the heat at home as was common in previous votes.