Tension was mounting in Mozambique on Monday with judges about to rule on its disputed election, with the opposition leader vowing "chaos" if the ruling party is confirmed as the winner in a standoff that has already claimed at least 130 lives.

The southern African country has been rocked by unrest since the election commission said that the October 9 vote was won by the candidate of the Frelimo party, which has held power since independence from Portugal in 1975.

The Constitutional Council is expected to announce at 3:00pm that it validates Frelimo's win, lining up Daniel Chapo to take over from President Filipe Nysui whose second term ends on January 15.

Businesses were shut and streets deserted in the capital Maputo early on Monday despite the fact that it is the height of the festive season.

The main roads into the city centre were barricaded by police and access to the presidential palace and Constitutional Council office shut, AFP journalists saw.

Opposition leader Venancio Mondlane claims the vote was rigged in favour of Frelimo and that a separate count shows he won enough votes to take office, which he intends to do.

Some had thought the opposition's challenge of the results was "a bluff...(that) we're joking," he told supporters on social media on Saturday. "So they will also be surprised on January 15 when they see Venancio Mondlane take office in Maputo."

Mondlane has been in self-imposed exile since the assassination of his lawyer on October 19, a killing he blames on security forces, and it was unclear if he intended to return.

"Difficult days will come," said the 50-year-old, who appeals to disenchanted younger voters in a country of 33 million people marked by poverty despite its abundant resources.

"The Constitutional Council's ruling will lead Mozambique either to peace or chaos," Mondlane said in an online address, promising a "new popular uprising at a level never seen before."

Game-changer

The dispute sparked an explosion of protests that have brought city centres to a standstill, disrupted industry and power plants, and halted operations at the main border with South Africa, causing its neighbour major losses in exports.

Police have been accused of using live bullets against protesters, with at least 130 people killed, according to the civil society group Plataforma Decide, whose figures have been cited by Amnesty International.

The US government on Thursday raised its warning level against travel to Mozambique ahead of the Constitutional Council announcement.

Pope Francis called Sunday for dialogue and goodwill to "prevail over mistrust and discord" in Mozambique.

President Nyusi and Mondlane had talked, both men confirmed last week, without announcing any outcome.

In an address to the nation on Friday, Nyusi said he hoped that once the final results were proclaimed, all sides "will open their hearts to a constructive and inclusive dialogue."

The preliminary results put Mondlane as runner-up in the presidential vote with 20 percent compared to 71 percent for Chapo. Mondlane claims a separate count shows he won 53 percent to 36 percent for Chapo.

The protests have been the "most dangerous" ever seen in Mozambique, said analyst Borges Nhamirre, continuing despite the deaths and arrests, and intensifying with police stations and Frelimo offices torched.

"Protests have already been called for Monday. The main cities, including Maputo, will be under siege because of the fear of protests," he said.

"I'm convinced that if Monday the Constitutional Council declares the election as free and fair, which I am 100 percent convinced it will, then the blood is going to flow," Maputo-based political and security risk analyst Johann Smith told AFP.

"The whole game changes on Monday," said Smith. "It will be a lot more intense and bloody."

Mondlane had awakened resentment against Frelimo, he said, similar to discontent that voted out this year the party that governed Botswana since independence and had threatened to do the same in Namibia.

"It's almost like the Southern African Spring," Smith said, in a reference to the Arab Spring anti-government protests in North Africa in the 2010s.

AFP