Britain and the US have called Venezuela's landmark vote a "sham" as 10 people - including two teenagers - were killed during violent protests.
Many in the South American country say it is heading for dictatorship and boycotted Sunday's vote for an assembly that would give President Nicolas Maduro virtually unlimited powers.
Opponents reacted with anger and mockery after the National Electoral Council said more than eight million people had voted.
With many polling stations deserted, rivals estimated the actual number was about two to three million.
Tear gas and rubber bullets were fired
An election candidate and an opposition leader were among those killed and a number of police officers were injured after an explosion in the capital Caracas.
Venezuelan soldiers fired rubber bullets and tear gas at people blocking a highway and the national guard, equipped with shotguns, patrolled the main roads.
Sky News' Stuart Ramsay was shot at as he stood near the demonstrations .
More than 120 people have been killed in four months of protests in Venezuela - which has seen living standards tumble in recent years despite its massive oil wealth.
Malnutrition has become a problem and people are struggling to get hold of basic products.
:: Oil rich but sliding into anarchy: Why is Venezuela on the brink?
President Maduro faced no opposition in the elections and people fear he will use the new 545-member assembly to rewrite the constitution, sack officials and tighten his grip on power.
Protesters say the President wants to create a dictatorship
Venezuelan President Nicolas Maduro cast his vote in Caracas
America's ambassador to the United Nations, Nikki Haley, said the election was a "step toward dictatorship" and that the US would not accept an illegitimate government.
"The Venezuelan people & democracy will prevail," she tweeted.
The US had also said it is considering oil-related sanctions against Venezuela, with measures announced "as early as Monday", according to officials.
Venezuela is the third-largest exporter of oil to the US, behind Canada and Saudi Arabia.
Many of the country's regional neighbours, such as Argentina and Mexico, have also condemned the vote.
People wore gas masks and armed themselves with shields
Stephen Gibbs, a journalist who covers Latin America, told Sky News that Mr Maduro "seems to be on a path towards not really caring about appearing - to a certain extent - a pariah state".
"He still has a few leftist governments in this region like Cuba, Bolivia and to a certain extent Ecuador, who are with him. But the big players are going against him."