Protesters rallied Monday vowing to block Venezuela's main roads to raise pressure on President Nicolas Maduro after three weeks of deadly unrest that have left 21 people dead.
Riot police fired rubber bullets and tear gas to break up one of the first rallies in eastern Caracas early Monday while other groups were gathering elsewhere, the opposition said.
It called for crowds to fill the main route into the capital and other roads around the nation.
That raised fears of fresh violence in an oil-rich country wracked by food shortages and political tension.
The center right-led opposition is demanding elections to get rid of Maduro, blaming him for the crisis.
It is furious at recent moves by authorities to curb his opponents' power.
Each side has accused the other of trying to mount a "coup."
Maduro has been resisting the opposition's drive to remove him for more than a year.
His critics brand him a dictator, while he says the crisis is a US-backed capitalist conspiracy.
"Peaceful protests across the country will continue until Mr Maduro respects the constitution and ends his internal coup," senior opposition leader Henrique Capriles tweeted Monday.
"If there is no answer from Maduro's corrupt drug-trafficking leadership, at the end of the day we will announce further action."
A presidential election is scheduled for 2018. Elections for regional governors due in December were postponed.
Maduro said Sunday he wanted the regional elections "now" but did not indicate a possible date for those or local ballots that are due this year.
"I am ready for whatever the electoral authorities say," insisted Maduro.
The government has ruled out an early presidential election this year as opposition leaders have demanded.
The socialist leader won the 2013 election by a narrow margin over Capriles. But Maduro's popularity has since dropped. A survey by pollster Venebarometro indicated that seven out of 10 Venezuelans disapprove of him.
The opposition blames Maduro for the unraveling of the oil giant's once-booming economy.
Falling oil prices have slashed its revenues, leading to critical shortages of food, medicine and basic goods.
Maduro resisted the opposition's efforts last year to hold a referendum on removing him from power.
Vatican-mediated negotiations between the two sides broke down.
Late last month, the authorities moved to seize the powers of the opposition-majority legislature, before reversing the measure. They later banned Capriles from politics.
The moves sparked international condemnation and a wave of opposition demonstrations from the start of the month.
The government and the opposition have accused each other of fomenting the deadly violence. Hundreds of people have been arrested or wounded and businesses looted.
Thursday saw shootings, looting and pitched battles in Caracas between demonstrators and police officers, who forced the evacuation of a maternity ward.
Eleven people died that day alone.
The latest victim, Almelina Carrillo, 47, on Sunday succumbed to injuries suffered when she was struck in the head by a bottle thrown from a building during one of the marches in Caracas last week.
Interior Minister Nestor Reverol called her "another victim of the Terrorist Right, which is full of hatred."
"We will not rest until we capture those responsible for this repugnant crime," he added.
The opposition has said it will use the momentum to keep taking to the streets, demanding elections and pushing for the release of political prisoners.
Maduro called the opposition to resume the dialogue, which broke down last year with the sides accusing each other of bad faith.
"I ask Pope Francis from here on out to continue to accompany us in the dialogue, because there is a conspiracy in Rome and here as well against dialogue in Venezuela," he said.