The official count gave runner-up Guy-Brice Parfait Kolelas 15 percent of the vote, while General Jean-Marie Michel Mokoko came in third with 14 percent.
Sassou Nguesso hailed the victory at his campaign headquarters, saying the Congolese people had "taken their destiny into their own hands" and adding that the campaign had produced a "very open" democratic debate in the former French colony.Both of his main rivals had already rejected the partial results released Wednesday, with Kolelas' spokesman Vivien Manangou saying there had been "massive fraud".
Mokoko, who until February was Sassou Nguesso's security advisor, added: "I knew beforehand that the dice were loaded, but we had agreed to play the game."
He called for a recount, saying: "How do you want us to accept such a result?"With telephones and the Internet cut off, neither candidate was immediately reachable after the official results were announced.
Oil- and timber-rich Congo has been on edge since an October constitutional referendum that ended a two-term limit on presidential mandates, allowing Sassou Nguesso, a 72-year-old former paratrooper colonel, to run for office again.Critics accuse him of rampant corruption and nepotism, blasting the referendum result as a "constitutional coup".
Authorities imposed a communications blackout during the election to prevent opposition candidates from publishing "illegal results". A government source said they blackout would remain in place until after the official results.
Most shops in the south of the capital Brazzaville, an opposition stronghold, had stayed shut on Wednesday amid fears of unrest.
Kolelas' spokesman Manangou said security forces had stormed the candidate's campaign offices on Tuesday, hurling tear gas cannisters and causing a stampede that left one person dead.
A French journalist was present but was unable to confirm the death.
Mokoko and Kolelas, along with the three other opposition candidates, have urged people to "exercise their sovereignty" in the event of a Sassou Nguesso victory.
They created their own parallel "technical commission" to monitor the vote and compile information from polling stations to compare it to the official results.
They said they could say "with certainty" that the opposition had beat Sassou Nguesso in the first round and that a second-round election should be held.
The European Union refused to send election observers to monitor the polls, saying conditions had not been met for a transparent and democratic vote.
The international community has since expressed concern over the fairness of the vote and called for the opposing sides to resolve their differences calmly.
"This vote took place in a worrying context, particularly due to the cut in communications," said France's foreign ministry spokesman Romain Nadal.