Venezuelan President Nicolas Maduro reacts following the presidential election results in Caracas on Monday. AFP

Venezuela's President Nicolas Maduro won re-election with 51.2 per cent of votes cast on Sunday, the electoral council announced, after a campaign tainted by claims of opposition intimidation and fears of fraud.

Elvis Amoroso, president of the CNE electoral body, in its majority loyal to the government, told reporters 44.2 per cent of votes had gone to opposition candidate Edmundo Gonzalez Urrutia.

Independent polls had predicted Sunday's vote would bring an end to 25 years of "Chavismo," the populist movement founded by Maduro's socialist predecessor and mentor, the late Hugo Chavez.

Maduro, 61, addressed supporters minutes after the announcement, saying: "there will be peace, stability and justice."

As his supporters celebrated, downcast opposition voters waited to hear from Gonzalez Urrutia and opposition leader Maria Corina Machado.

US Secretary of State Antony Blinken immediately expressed "serious concerns" that the result did not reflect the will of Venezuelan voters.

Venezuelan opposition leader Maria Corina Machado talks to the media in Caracas on Monday. AFP

Since 2013, Maduro has been at the helm of the once wealthy petro-state where GDP dropped by 80 per cent in a decade, pushing more than seven million of its 30 million citizens to emigrate.

He is accused of locking up critics and harassing the opposition in a climate of rising authoritarianism.

Gonzalez Urrutia had replaced popular Machado on the ticket after authorities loyal to Maduro excluded her from the race.

Machado, who campaigned far and wide for her proxy, had urged voters on Sunday to keep "vigil" at their polling stations in the "decisive hours" of counting amid widespread fears of fraud.

Maduro had previously warned of a "bloodbath" if he loses.

'Prepared to defend'

Rejecting opinion polls, the government relied on its own numbers to assert Maduro would defeat Gonzalez Urrutia, a little-known 74-year-old former diplomat.

Maduro counts on a loyal electoral apparatus, military leadership and state institutions in a system of well-established political patronage.

Venezuelan President Nicolas Maduro celebrates with supporters in Caracas on Monday. AFP

On Friday, a Venezuelan NGO said Caracas was holding 305 "political prisoners" and had arrested 135 people with links to the opposition campaign since January.

Gonzalez Urrutia had said the opposition was "prepared to defend" the vote and trusted "our armed forces to respect the decision of our people."

He added there had been a "massive" voter turnout.

Ballots were cast on machines which print out paper receipts placed into a container. The electronic votes go directly to a centralized CNE database.

The opposition had deployed about 90,000 volunteer election monitors to polling stations countrywide.

Watching 'very closely'

Sunday's election is the product of a mediated deal reached last year between the government and opposition.

The agreement to hold the vote led the United States to temporarily ease sanctions imposed after Maduro's 2018 reelection, which was rejected as a sham by dozens of Western and Latin American countries.

But the sanctions were snapped back after Maduro reneged on agreed conditions.

Venezuelans react after the results of the presidential election, outside Venezuela's Embassy in Mexico City. Reuters

Washington is keen for a return to stability in Venezuela -- an ally of Cuba, Russia and China that boasts the world's largest oil reserves but severely diminished production capacity.

Economic misery in the South American nation has been a major source of migration pressure on the US southern border.

Most Venezuelans live on just a few dollars a month, with the country's health care and education systems in disrepair and the population enduring biting shortages of electricity and fuel.

The government blames sanctions, but observers also point the finger at corruption and government inefficiency.

Machado said earlier Sunday that if Maduro "grabs power," another "three, four, five million" Venezuelans will likely join the exodus.

"What's at stake here goes beyond our borders, beyond Venezuela," she said.

Concerns over the fairness of the vote were further stoked when Caracas blocked several international observers, including four Latin American ex-presidents, at the last minute.

The foreign ministers of seven Latin American nations called Sunday for the electoral process to "fully respect the popular will" of the Venezuelan people.

About 21 million Venezuelans are registered as voters, but only an estimated 17 million still in the country were eligible to cast ballots.

Agence France-Presse