The Venezuelan authorities have been criticised for the way they have been checking signatures for a referendum on President Hugo Chavez's rule.
Protesters believe the government is ignoring the poll result
The Organisation of American States said it was unhappy that only some of the results have been published.
Protests erupted across the country on Tuesday after officials said the president's opponents had failed to force a referendum.
At least one demonstrator was killed in unrest in the capital, Caracas.
The opposition has rejected the National Electoral Council's announcement which stated that so far not there were enough signatures for a referendum to go ahead.
The National Electoral Council said only 1.8m signatures calling for a referendum had been verified, but another 870,000 were disputed.
The opposition needs 2.4m to force the vote on leftist President Hugo Chavez.
It could still reach this target - the council has said it will publish lists of the disputed signatures and set up posts where people who find themselves on these listings can go and validate their entry.
But the opposition has accused the president of trying to prevent a referendum and the electoral council of favouring him.
Senior opposition figures have already said they will not accept the electoral commission's plans for voters to confirm their signatures, complaining this was not included in the initial rules for the referendum.
"There is no other way but to accept this decision," responded election official Francisco Carrasquero. "If someone does not accept it, they will be acting outside the law."
Soldiers in armoured carriers maintained a stand-off with anti-Chavez protesters in several cities across Venezuela, including Valencia, Barquisimeto and Maracaibo.
Witnesses report petrol bombs, stones and tear-gas shells flying across improvised barricades of burning tyres.
Hugo Chavez's supporters say he has helped the country's poor
The government urged opposition mayors to end the rioting.
"It's amazing to see how some mayors are allowing the destruction of their own municipalities," said government security official Carlos Valter Bettid.
Venezuelans who backed the plebiscite against President Chavez have been protesting for days.
They were told on Tuesday it could take three weeks for more signatures to be gathered to confirm the poll result.