At least 21 people have been killed in the southern African nation of Mozambique since Monday, a government official said, as police officers and protesters clashed in the latest wave of unrest over a presidential election that demonstrators claim was rigged by the governing party.

Speaking at a news conference on Tuesday, the official, Pascoal Ronda, Mozambique’s interior minister, did not provide details on how the deaths occurred. He said two police officers were among the dead and that authorities had made 71 arrests in connection with the violence.

Human rights groups have asserted that Mozambique’s security forces have responded with excessive force to protests that erupted after the October election, including by firing live rounds and rubber bullets into crowds. More than 100 people have died in sporadic protests since the election was held.

Tensions escalated this week after the nation’s top court on Monday upheld the result of the election in favor of Daniel Chapo, the candidate for Frelimo, which has governed Mozambique since it gained independence from Portugal in 1975.

Protesters responded to the ruling by burning tires and blocking roads with rubbish and streetlights. Mr. Ronda said that hundreds of buildings were looted and vandalized, including police stations, schools, hospitals, courts and homes. A penitentiary was attacked, and 86 inmates were released.

“These acts pose a direct threat to stability, public safety and the values of our young democracy,” Mr. Ronda said. “Defense and security forces must act firmly to restore normalcy and hold those responsible accountable.”