The death toll climbed to 49 as the unrest entered its eighth week, the public prosecution service said in a new toll.
Fresh clashes broke out between protesters and police early Monday on the outskirts of Caracas, where demonstrators blocked streets with barricades.
After marches by various civil groups, it was the turn of the Venezuelan Medical Federation to vent its frustrations in the streets.
More than a thousand of its sympathizers marched towards the health ministry in Caracas. Police fired tear gas to drive them back, in scenes familiar after weeks of unrest.
"The country is verging on catastrophe. The health system is a disaster," said Fernando Gudayol, a 50-year-old surgeon.
"One is always afraid to come out, but we will carry on doing it until there is a change."
Maduro criticises protesters
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Pro-government counter-rally
The opposition is demanding elections to remove Maduro from power. They blame him for an economic crisis that has caused shortages of food, medicine and basic supplies.
"A simple infection can turn into something serious for a lack of antibiotics and any kind of supplies, and for a lack of maintenance of the equipment," said Eliecer Melear, a 41-year-old urologist.
Maduro's supporters staged a counter-demonstration near the presidential palace.
"What lack of medicine?" asked medical student Rangel Vegas, 31. "We are in the streets and in the clinics giving a response to what communities need."
Maduro called for a further "march for peace" on Tuesday.
Man set alight
In the latest gruesome unrest on Sunday, a man was beaten, doused in petrol and set alight during a protest in the capital Caracas, an AFP photographer saw.
Some witnesses alleged the man was a thief, but the government later said he was attacked for being a Maduro supporter.
Speaking later on television, the president identified the man as Orlando Figuera, 21. He said he was hospitalized with first- and second-degree burns over half of his body and six knife wounds.
Maduro accuses the opposition of plotting a coup against him with US backing. He says the crisis is a capitalist conspiracy.
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Opposition risks 'losing steam'
Elected in 2013, Maduro has resisted opposition efforts to remove him since January 2016.
He has said there will be presidential elections as scheduled next year, but not before.
Instead, he has angered the opposition by seeking constitutional reforms which his rivals say aim to strengthen his grip on power.
Maduro retains the public backing of the military and control of most state institutions.
Street protests and international pressure "could lead to divisions within the government or within the armed forces or between the government and the armed forces," said David Smilde, a Venezuela expert at the Washington Office on Latin America, a nongovernmental organization.
But he added: "It is hard to keep protest waves going. People have to work, study, eat and live their lives. The opposition needs to think about how to consolidate their gains. Otherwise, this movement too could lose steam."
