Supporters of Mozambique's opposition leader Venâncio Mondlane have been injured as police tried to break up the crowds who had come to meet him after his return from self-imposed exile on Thursday.

He had left the country saying he thought his life was in danger following October's disputed presidential election that sparked deadly protests.

Mondlane landed at the main airport in the capital, Maputo, amid tension and heavy security, with thousands having gathered to welcome him.

His return came ahead of next week's swearing-in of Daniel Chapo as president. He was the candidate of the ruling Frelimo party and was confirmed as the winner of October's poll by the constitutional court.

The final official results declared by the country's highest court just over a fortnight ago gave Chapo 65% of the vote and Mondlane, in second place, with 24%.

Frelimo has been in power for the past five decades since independence from Portugal.

After having emerged from the airport building, the video shows Mondlane kneeling on the ground with a Bible in his hand being cheered by supporters.

The 50-year-old Pentecostal preacher began to pray and then said that he had won the election.

"I, Venancio Mondlane, president-elect by the Mozambican people… elected by the genuine will of the people – swear on my honour to serve the Mozambican homeland and its people," he declared.

He said he was returning to be closer to the protest movement that has seen weeks of nationwide demonstrations in which dozens of people have been killed.

On Thursday, three people were shot and injured at one of the capital's markets following a brief rally held by Mondlane, police spokesperson, Orlando Mudumane said.

Witnesses said that as the police were trying to disperse the crowd shots were fired. Those injured were then taken to hospital.

There are other unconfirmed reports of fatalities.

The police spokesperson also told journalists that two off-duty officers had been attacked and killed in another province - Nampula.

In his first comments on arrival in the country, Mondlane said that he was ready to talk about how to resolve the tension over the disputed poll, which he says was stolen from him.

"I'm here in the flesh to say that if you want to negotiate... I'm here," he said.

He added that he had come back to speak out against "atrocities" which he said were being committed against his supporters and to defend himself against allegations of criminal responsibility.

He also said he would "continue fighting for this country and preventing the continuation of the current situation".

Mondlane has been organising protests through broadcasts on Facebook, but over the weekend announced his impending return, saying they "don't need to chase me anymore".

In a defiant message, he said: "If [the authorities] want they can kill me, but the fight will continue".

Ahead of his landing, the airport was heavily guarded with police officers trying to prevent Mondlane's supporters from reaching the area.

Mondlane said his return was "a unilateral decision" that did not result from any political agreement. He has previously said he would install himself as president on 15 January.

Since the October election, waves of protests have left more than 270 people including protesters, children and members of the security forces dead, according to rights groups.

The protests and the violent crackdown by security forces have tested the country's stability and there have been concerns that would worsen should anything happen to Mondlane.