Pro- and anti-government rallies totalling hundreds of thousands of people jammed Caracas, the capital of Venezuela, on Monday.
Supporters of President Nicolas Maduro accused opponents of trying to foment a coup d'état, but opposition leaders promised to continue protests that have shut down major cities over the past month.
Some ordinary Venezuelans have tired of the constant opposition street blockades that have made it impossible to visit a doctor, go to work or attend school.
Taxi driver Jesus Jaime criticized the opposition tactics because he can't earn a living. On one day of blockages, he said, "I didn't get even a single fare. And I was waiting for eight hours at my taxi stand."
The political crisis began in late March when the Venezuelan Supreme Court dissolved the opposition-controlled National Assembly. Although the decision was quickly reversed, it led to large street demonstrations by the opposition coalition known as the Democratic Unity Roundtable (MUD).
Henrique Capriles, a state governor and top MUD leader, said the opposition wants the release of political prisoners and immediate scheduling of elections, among other demands.
"The government doesn't want to have elections in Venezuela," he said in an interview. "That's unacceptable."
Also on Monday, Maduro announced a vote for a new popular assembly with the capacity to rewrite the constitution, but foes said it was an attempt to cling to power amid major protests.
'I don't want a civil war.' — Venezuelan President Nicolas Maduro
"I don't want a civil war," Maduro told a May Day rally of supporters in downtown Caracas, while elsewhere across the city security forces fired tear gas at youths hurling stones and gasoline bombs after opposition marches were blocked.
Maduro has triggered an article of the constitution that allows for the reformation of all public powers, as his predecessor Hugo Chavez did in 1999 soon after winning office in the South American OPEC nation.
But Capriles argued that Maduro has become a dictator, and is increasingly isolated at home and internationally. He promised to continue organizing peaceful demonstrations.
"Now we have a perfect storm that didn't exist before," he said.
While MUD proclaims its peaceful intentions, increasing numbers of Venezuelans are upset with the violent clashes it has provoked. Opposition youth regularly throw stones and gasoline bombs at government security forces, and even burned the administrative offices of the Supreme Court on April 8.
On April 26 several hundred youth chanting opposition slogans threw stones and set fires at a government-operated maternity hospital, forcing the evacuation of 54 women and children, according to five witnesses and hospital staff interviewed by CBC News.
Freddy Guevara, vice-president of the National Assembly and another major opposition leader, acknowledged some violent activity but blamed it on government provocateurs and hotheads. "Young people are angry and frustrated about the repression," he said in an interview.
Several dozen protestors have been killed with gunshots and tear gas canisters. Armed bands of pro-government "collectivos" have attacked opposition neighbourhoods and people seen as collaborators.
One pro-government activist appalled by the violence wrote in an email about a friend who was shot by a collectivo. "Several of the assassins on motorcycles proceeded to strip and robbed his dying body," she wrote. "The roaming armed military/civilian gang moved into a nearby opposition demonstration, wounding several others."
In the face of such attacks, the opposition is seeking greater international support. The Organization of American States has sharply criticized the Maduro government. In late April Venezuela announced plans to withdraw from that body.
U.S. President Donald Trump has supported the opposition by meeting with the wife of a jailed opposition leader. The U.S. Justice Department indicted Venezuela's vice-president on drug-running charges.
Opposition leader Capriles appealed for additional outside support, arguing that Venezuela's crisis goes beyond a fight between the government and MUD. He said the entire continent could be destabilized if Maduro stays in power.
"Don't underestimate it," he said.
On the other hand, government supporters argue that neither U.S. pressure nor continuing street protests will topple Maduro. Indeed, the opposition may resort to a military coup d'état, according to Reinaldo Iturriza, a former minister of culture.
"The opposition is trying to foment divisions in the military," he said in an interview.
Iturriza said the opposition would welcome a coup if it brought their leaders to power.
"I wouldn't be surprised if an active duty officer appeared on TV to denounce the government," he said.
Capriles argued that "there's a lot of discontent in the military." But he denied any efforts to use undemocratic methods to topple the government. "We don't want a coup nor do we want a military uprising," he said.
So far the military shows no signs of backing the opposition. Unlike some Latin American countries, the Venezuelan military has a 20-year history of support for the leftist government and its Bolivarian Revolution, the term used to describe Venezuelan-style socialism.
Hugo Chavez, who founded the Bolivarian movement and served as president from 1998 until his death in 2013, was himself a career military officer.
But high unemployment, inflation and shortages of food and medicine are increasing tensions in the country. Disruptive demonstrations appear likely to continue.