Venezuela's acting president Nicolas Maduro scored a surprisingly narrow victory in Sunday's special election to succeed the late Hugo Chavez.
The national election authority announced the Maduro victory over opposition leader Henrique Capriles, hours after the polls closed across the South American country.
Maduro supporters gathered in the streets of the capital of Caracas to celebrate the election of Mr. Chavez's hand-picked successor. The 50-year-old former bus driver and foreign minister told the crowd the "fight" to continue Mr. Chavez's legacy continues.
Mr. Capriles has refused to accept the results, denouncing the final vote tally as illegitimate and calling for a recount.
Cuban President Raul Castro was among the first to congratulate Mr. Maduro in a statement published in the Communist Party newspaper Granma.
Mr. Maduro began the campaign with a double-digit lead in the polls over Mr. Capriles, a 40-year-old state governor who lost decisively to Mr. Chavez in last year's presidential election.
But Mr. Maduro's lead shrank considerably in the lead-up to Sunday's vote. Mr. Capriles accused the Maduro and Chavez government of doing little to solve Venezuela's economic problems, food shortages and soaring crime rate.
Mr. Maduro has pledged to continue what he calls the Chavez revolution, which supporters say used oil wealth to lift millions out of poverty.
Mr. Chavez died last month after a two-year battle with cancer.
He was a staunch socialist who was first elected president in 1998. He earned the enmity of the United States and others for such policies as nationalizing major companies and courting world leaders like Cuba's Fidel Castro, Iran's Mahmoud Ahmadinejad and Libya's Moammar Gadhafi.
The opposition accused him of becoming a dictator, but he was revered by many of Venezuela's poor.