Dozens of hardcore protesters in Caracas threw rocks and lobbed firebombs at riot police who retaliated with tear gas Monday, after Venezuela's opposition upped the ante on President Nicolas Maduro.

At least three people were detained in the clashes in a middle-class district of the capital, on the eve of the one-month anniversary since the start of nationwide protests, said the director of the non-governmental Venezuelan Penal Forum, Alfredo Romero.

Thousands of Venezuelans dressed in white, blowing on whistles and blasting horns, protested in Caracas Sunday against the government of President Nicolas Maduro, the latest in escalating demonstrations that have left 18 people dead.

Hours earlier, authorities released dozens of protesters and an Italian photographer, but that did nothing to appease demonstrators angry at a soaring crime rate, spiraling inflation, the lack of basic goods and limited democratic rights.

Venezuela's foreign minister will meet Tuesday with U.N. Secretary-General Ban Ki-moon in Geneva to discuss three weeks of deadly protests that have rattled the oil-rich country.

Fresh anti-government demonstrations took place Saturday, with protesters calling for the release of dozens of activists who have been arrested in the protests that have left 18 people dead.

Time was, overturning a freely-elected government would have earned a sharp U.S. rebuke. But as people power revolts sweep some countries, Washington is increasingly giving its blessing to ousting leaders accused of betraying democracy.

From Egypt, where the nation's first democratically-elected president Islamist leader Mohammed Morsi was toppled in July by the army, to Ukraine where Viktor Yanukovych, brought to power in 2010 polls, fled his post after months of street protests, the U.S. has had to fine-tune its response.

Anti-government protesters took to the streets of Venezuela's capital on Saturday, calling for the release of dozens of activists who have been arrested during three weeks of violent demonstrations.

Protesters from a radical opposition group formed a convoy of cars and bikes in eastern Caracas after fresh violence on Friday saw pitched battles between security forces and demonstrators.

At least 41 people, including foreign reporters, were arrested in Caracas late Friday as security forces battled protesters angry at the policies of Venezuela's leftist government.

National Guard security forces blasted the student-led demonstrators with high-pressure water and fired tear gas canisters into the crowds in an attempt to break up the protest. Hooded protesters set up barricades and responded by hurling rocks and Molotov cocktails.

Weeks of protests in ally Venezuela are reviving the concerns of many Cubans dependent on the largesse of the socialist Caracas government while buoying the opposition on the communist island.

Venezuelan President Nicolas Maduro is facing his biggest test since succeeding the late Hugo Chavez last year in a narrowly won election, with near-daily demonstrations against his administration leaving 17 people dead since early February.

Venezuelan Foreign Minister Elias Jaua on Friday said his government has Brazil's support for a meeting of the South American Unasur group to discuss instability in his country.

Denouncing the protests that have swept Venezuela since February 4, leaving at least 17 dead, Jaua said Brazil had reacted positively to his call for a Unasur meeting.

U.S. Secretary of State John Kerry on Friday called on Venezuelan leaders to start talking to their own people and stop a wave of opposition arrests.

"It seems to me what has to happen now is for (the) Venezuelan leadership to deal with their own people," Kerry told reporters.

The death toll from more than three weeks of political unrest in Venezuela has risen to 17, Attorney General Luisa Ortega said Friday.

She told reporters that another 261 people have been injured in the violence that has accompanied large protests against the government of President Nicolas Maduro.