MAPUTO, Mozambique — Gunmen in two vehicles ambushed the lawyer for Mozambique’s leading opposition politician and a senior opposition official, shooting them dead in their SUV late at night on a main avenue in the capital, their party said Saturday. The brutal burst of violence rocked a country where tensions were already high amid a disputed election.

The killings came as the opposition party the two men were associated with prepared to challenge the results of this month’s presidential election that drew more allegations of vote rigging and clamping down on dissent against the governing party, which has been in power for nearly 50 years.

Elvino Dias, a lawyer and advisor to opposition presidential candidate Venancio Mondlane, was killed late Friday night when gunmen riddled his car with bullets in the port capital of Maputo, the PODEMOS opposition party said.

Paulo Guambe, the spokesperson for PODEMOS, was also in the car and was killed, the party said in a statement.

The killings are “further clear evidence of the lack of justice that we are all subjected to,” PODEMOS said.

Police said a woman who was in the car was injured and was being treated in a hospital. Police spokesperson Leonel Muchina said the victims had earlier been at a local bar and were followed from there. Muchina said the killings might be related to interactions the two men had with other patrons at the bar.

The shootings were widely viewed in Mozambique as being politically motivated, however.

PODEMOS is a relatively new opposition party that challenged the 49-year rule of the Front for the Liberation of Mozambique, or Frelimo, party in the Oct. 9 election.

Although Mondlane ran for president as an independent, he was supported by PODEMOS. Mondlane, PODEMOS and other opposition parties have accused Frelimo of electoral fraud and rigging the election.

Frelimo candidate Daniel Chapo holds a clear lead in the presidential race, with Mondlane second, according to preliminary results.

The final election results are due next week and Chapo is expected to be announced as the winner to succeed President Filipe Nyusi, who has served the maximum of two terms allowed under the constitution.

Dias was seen as a key figure in the legal preparations to challenge the results in the Constitutional Council, Mozambique’s supreme electoral court. Mondlane and PODEMOS had also called for a nationwide strike and protests on Monday.

Adriano Nuvunga, the director of the Centre for Democracy and Development, a Mozambican human rights NGO, wrote on social media that the killing of Dias was a “political assassination” amid rising tensions.

Dias posted on Facebook in April that he had been warned by a friend that he and Mondlane might be in danger because of their criticism of the ruling party. Dias said in the post that both had decided to continue their work because “it was the life option we chose; be on the side of truth and justice.”

Frelimo, which has been in power in the southern African country since independence from Portugal in 1975, has often been accused of rigging elections, which it has consistently denied.

Rights groups accused Mozambican authorities of clamping down on dissent in the run-up to the election and have also accused the security forces of using deadly force to break up peaceful protests. Police broke up a post-election march by Mondlane supporters in the central city of Nampula earlier this week. There has been a large police presence on the streets of Maputo for days.

While Frelimo has regularly faced accusations of manipulating elections, harassing the opposition and arresting journalists, the assassination of political leaders would be new “and a major escalation of violence,” Marcelo Mosse, editor of the independent online newspaper Carta de Moçambique, wrote in a Saturday morning column.

The shooting happened just before midnight on Joaquim Chissano Avenue near the Russian Embassy, according to a local resident, who said he heard the gunshots. The resident, who asked not to be identified, said he heard a steady sequence of around five shots, followed a few seconds later by another round of five shots.

Videos published on social media showed a dark gray BMW SUV in the middle of the road with numerous bullet holes in the bodywork. People were gathered around the car soon after the shooting, and some of the videos showed what appeared to be the bodies of two men, one with blood on his chest, in the front seats. The other body was slumped over.

The Mozambican Bar Association condemned the “barbaric murder” of Dias, who had been a member. The organization said the killing was “an attack on the legal profession, its independence, the rule of law and democracy,” and called for a protest march to be held in all provinces.

Frelimo established a one-party state following independence and then fought a bloody, 15-year civil war against the rebel group Renamo. They signed a peace deal in 1992 and Renamo became the main opposition party following Mozambique’s first democratic elections in 1994, but the peace between them has been fragile.

Mondlane was previously a member of the Renamo party but left to run for president as an independent, becoming the leading opposition candidate and a new challenge to Frelimo.