Security forces in riot vans blocked off central Caracas Monday as Venezuela braced for pro- and anti-government May Day protests one month after a wave of deadly political unrest erupted.
Opposition leaders vowed no let-up in their protests demanding elections to get rid of President Nicolas Maduro.
They blame him for an economic crisis that has caused shortages of food and medicine.
Clashes between protesters and riot police left 28 people dead last month, according to prosecutors.
"The regime is betting that we will tire ourselves out. That is why, after one month of resistance, we must show our strength," said senior opposition lawmaker Freddy Guevara.
- May Day protests -
Maduro's supporters planned to stage their traditional Workers' Day rally in Bolivar Square in the central pro-government district of the capital.
"We are marching in support of Maduro and to defend the conquests of the revolution," said Edmundo Marcano, 55.
May Day demonstrations in defense of workers' rights are traditionally a show of support for the socialist government.
But the opposition vowed to defy that by marching towards the nearby Supreme Court and electoral council.
Attempts to do so over recent weeks have sparked clashes with police.
"I am out fighting for Maduro to go. This is a dictatorship in disguise," said Matilde Rodriguez, 67, from the working class Petare district of Caracas.
"Venezuela is in intensive care. There is no food and they'll kill you for a pair of shoes."
Security forces put up metal barriers in the center to block access for the opposition. Some 30 metro stations were shut down.
"The first of May belongs to the working class. It is not a day of capitalism or the right wing," Maduro said on Sunday.
Senior opposition leader Henrique Capriles retorted: "The biggest and most historic announcement Maduro could make for the workers and for the country would be to leave power."
- Month of unrest -
Protesters took to the streets from April 1 to demand elections after the Supreme Court tried to strengthen Maduro's grip on power.
The opposition has accused him of installing a dictatorship.
Even residents of traditionally pro-Maduro districts have been joining in the protests against him in recent days.
Maduro says the economic crisis in his major oil-exporting nation is a US-backed capitalist conspiracy.
The Venezuelan president has vowed to continue the socialist "Bolivarian revolution" launched by his late predecessor Hugo Chavez.
Last month's violence was "an ambush... to impose a violent counter-revolution in Venezuela," he said on Sunday in a television broadcast.
He marked Workers' Day by raising the minimum wage 60 percent. That brought it to $280 a day at the highest fixed exchange rate.
The International Monetary Fund estimates Venezuela's inflation rate will hit 720 percent this year.
- Election demand -
Maduro has rejected opposition calls for general elections before his term ends late next year.
He has said he is willing to hold regional polls that were postponed in December.
But the electoral authorities have not set a date and electoral prospects for the center-right opposition coalition look slim.
Popular Will party leader Leopoldo Lopez is in jail. Capriles of the Justice First party has been banned from politics by authorities.
Yet aside from dangerous street protests, regional elections this year may be their only remaining lever for pressuring Maduro.
"We have to combine the elections with resistance in the street to change the government," said Miguel Pizarro, an opposition lawmaker.
Maduro on Sunday welcomed an offer by Pope Francis of Vatican mediation for dialogue between the sides.
But opposition leaders rebuffed the overture, insisting there must be a timetable for general elections.
© 2017 AFP