The governments of the United States, Brazil, Argentina and Colombia proposed a second round in the Bolivian elections after incumbent President Evo Morales was controversially declared the winner on Thursday.
The group of countries called on Bolivia's government "to restore credibility in its electoral system" by giving voters another chance to choose between socialist Morales and centrist former president Carlos Mesa.
With 99.99 percent of the ballots counted, the country’s Supreme Electoral Tribunal (TSE) declared Morales had secured 47.1 percent of the vote, against 36.5 percent for his closest rival Mesa – just scraping past the 10 point margin of victory required for an outright win.
Mesa accused Morales and his government of fraud. “We are in a crucial moment of history,” he said in a video delivered to AFP by his press team.
Observers from the Organisation of American States have expressed concern over the vote count, which triggered riots, a general strike and opposition accusations of fraud.
The European Union said Thursday it shared the OAS assessment "that the best option would be to hold a second round to restore trust and ensure the full respect of the democratic choice of the Bolivian people."
Violent protests have raged all week, and fresh clashes broke out Thursday between supporters of both sides in Santa Cruz, the economic capital and opposition stronghold.
Offices in the city housing Bolivia's electoral authority were set on fire overnight, as security forces clashed with demonstrators in La Paz and elsewhere.
The new mandate means Morales, already Latin America's longest-serving president, would remain in power until 2025.
He stood for a fourth successive term despite Bolivia's constitution limiting presidents to two consecutive mandates.
Mesa accused Morales's party, the Movement for Socialism (MAS), of "electoral fraud" after it declared Morales the winner before official results were announced.
Speaking at a rally in La Paz earlier Thursday alongside centre and right wing parties as well as business leaders, Mesa called for a second round and urged his supporters to maintain pressure in the streets.
On Wednesday he said he would not recognise results tallied by the tribunal, which he accused of manipulating the count to help Morales win.
The TSE has been heavily criticised for its conduct of the count process, including by its own vice-president, who resigned.
The governments of the United States, Brazil, Argentina and Colombia all called on Bolivia's government "to restore credibility in its electoral system" by allowing a second round run-off.
The US State Department updated its travel alert for Bolivia, urging "increased caution... due to civil unrest."
On Monday, after the release of partial election results showed Morales just ahead of Mesa, mobs torched electoral offices in Sucre and Potosi, while rival supporters clashed in La Paz.