HARARE, Zimbabwe -- Zimbabwe opposition leader Nelson Chamisa on Friday forcefully rejected the narrow election win of President Emmerson Mnangagwa as fraudulent, calling it a vote "stolen from the people."

For his part, Mnangagwa praised the vote as "free, fair and credible ... an unprecedented flowering of freedom and democracy in our beloved homeland" as the country seeks to move beyond Robert Mugabe's decades-long rule.

The opposition said it will challenge in court the results of Monday's election, which Mnangagwa won with just over 50 percent of the vote. The closely watched elections began with a peaceful vote but turned deadly 48 hours later when the military fired on protesters in the capital, Harare, and six people were killed.

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The 40-year-old Chamisa spoke shortly after three truckloads of riot police with shields and batons tried to disperse dozens of journalists gathered to hear him. With cameras recording their every move the police eventually pulled back, allowing the opposition leader to give a blistering denunciation of the results.

"We won this election," Chamisa said, declaring "a day of mourning ... for democracy." He alleged violence and harassment against his supporters.

Chamisa received over 44 percent of the vote but claimed that based on the opposition's own count he won 56 percent. He was asked for evidence but didn't share it, instead saying the electoral commission "didn't want to listen to us."

Mnangagwa said people are free to challenge the vote in court. Speaking to the press, he said Chamisa has a "crucial" role to play in the country's future.

Zimbabweans had a subdued reaction to Mnangagwa's win in the first election after the fall of Mugabe, whose rule was marked by increasing repression and the economy's collapse.

The 75-year-old Mnangagwa, Mugabe's former enforcer and confidante, said he was "humbled" by the victory.

The president called the violence on Wednesday "unfortunate" and said the military was called in because vehicles were burned and lives were threatened. He said he will order an independent investigation by "people of integrity" in Zimbabwe and abroad.

Troops were no longer visible on the streets of Harare but water cannons and police remained present at the headquarters of the main opposition party a day after authorities raided it and made 18 arrests. Chamisa accused police of seeking what he called evidence of vote-rigging.

The week's events left many Zimbabweans with a sense of unease and questions about how different Mnangagwa is from his predecessor Mugabe, who stepped down in November under military pressure amid a ruling party feud after 37 years in power.

A police vehicle in central Harare was heard broadcasting messages through a loudspeaker.

"Zimbabwe is open for business. We are here to protect you. Feel free to walk and open your business. All is well, fear not," the messages said, according to BBC News.

The 75-year-old Mnangagwa has tried to recast himself as a voice of change, inviting the Western election observers who for years had been banned by Mugabe.

If this election is judged credible, it will be a big step toward the lifting of international sanctions on this southern African nation whose economy has long collapsed and whose reputation has suffered after years of repression of the opposition and allegedly rigged votes.

So far international observers have issued mixed reviews, calling Monday's election peaceful and a break from the past but expressing grave concern about the military's "excessive" use of force. They criticized the delay in releasing the results of the presidential vote, saying it raised concerns about possible manipulation.

Some observers from the Commonwealth watched from a rooftop and windows as the riot police dispersed journalists ahead of Chamisa's briefing. Margaret Jay, one of the observers, called it another example of the "excessive use of force in political situations" by Zimbabwean authorities.

Anxious Zimbabweans waited to see what would happen next. In Kuwadzana, a poor suburb outside the capital where groups of youths overnight sang and chanted MDC slogans before results were announced, it was silent.

One street vendor in the capital, Roy Mukwena, said Mnangagwa "won by force. No, I'm not happy, just because these elections were not free and fair."

Some, however, were content to move on and deal with the new leader.

"Yeah, I think he's the right man. Because he has been there for quite some time and he knows where the weaknesses are," said a 29-year-old clerk who gave his name only as Eddy. "He has the experience from ... previous government. So he knows how to maneuver all the problems we have. I just hope he will do well."