Opposition protesters chanting "No more dictatorship!" hurled stones at National Guard riot police who blocked them from marching on central Caracas.
The police responded with tear gas and water cannons, prompting chaos on the eight-lane highway where some 10,000 protesters had tried to break through security barricades.
Dozens of protesters were wounded, and at least six arrested, said AFP journalists on scene.
Scores of protesters were also wounded at violent protests on Tuesday and Wednesday in the volatile oil-exporting country, where a political crisis is raising concerns about democracy and stability.
Street protests are among the few options left for the center-right opposition to pressure Maduro, whom they blame for the country's descent into economic calamity.
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Venezuela court retreats from bid to boost president's power
Negotiations have failed and he has resisted international pressure, while retaining backing from the military and control over most state institutions.
The opposition has taken to the streets accusing pro-Maduro Supreme Court judges of attempting an internal "coup d'etat" for attempting to take over the opposition-majority legislature's powers last week.
The socialist president's supporters held counter-demonstrations on Thursday, condemning Maduro's opponents as "imperialists" plotting with the United States to oust him.
Maduro himself downplayed the unrest.
"Venezuela is at peace, producing, working, with small flashpoints of violence. They were neutralized under constitutional authority, and they failed in their objective: to fill Caracas with violence," he said on state television.
'Tired of dictatorship'
Last week, the Supreme Court issued rulings transferring the National Assembly's legislative powers to itself and revoking lawmakers' immunity from prosecution.
The court later reversed the rulings after an international outcry, but kept in place other measures limiting the assembly's powers.
Opposition lawmakers launched an effort to impeach the judges on Wednesday.
But that would require a green light from the attorney general, prosecutor general and comptroller, all Maduro allies.
They refused Thursday to give the go-ahead -- though the attorney general had sharply criticized the Supreme Court rulings, in a rare display of dissent in Maduro's camp.
On the streets, protesters said they want to get rid of Maduro.
"We're tired of this dictatorship," said Yoleidy Rodriguez, a 22-year-old university student. "We're not afraid."
A group of protesters eventually managed to march up to the metal police barricade, their hands in the air, and spray paint "Freedom" on it in blue letters.
An opposition politician, Roberto Enriquez, meanwhile fled to the Chilean ambassador's residence in Caracas, alleging political persecution.
Chile vowed to protect Enriquez, the head of the Christian social democratic party, whom Maduro's allies accused of plotting a coup.
Days of protest
Scores of people were hurt on Tuesday when riot police used tear gas and water cannons to disperse a protest march in Caracas, opposition groups said.
On Wednesday, similar clashes broke out in the western city of San Cristobal, the scene of deadly riots and looting last year, and in the city of Valencia.
The wave of protests has revived fears of broader unrest in Venezuela, where 43 people were killed during riots in 2014.
The country has undergone three attempted military coups since 1992.
Election pressure
Maduro is resisting opposition efforts to hold a vote on removing him from power.
Venezuela's next general election is due in December 2018. Regional elections last December were postponed indefinitely, and no date has been set for local polls due this year.
The collapse in energy prices has sapped the country's revenues, prompting shortages of food, medicine and basic goods along with a surge in violent crime.
The opposition blames Maduro for the economic crisis. He says it is due to a capitalist conspiracy.
Although he has retained the crucial support of the army so far, that could be changing, political analyst Luis Salamanca said.
"At this point, Maduro can't say he's sure of anyone's support," he said, "including the armed forces."
