Venezuelan opposition leader Juan Guaido on Saturday launched what he promised will be a "definitive" escalation of pressure to force the country's embattled leftist leader from office.
Addressing a huge anti-government rally in Caracas, Mr Guaido – whose claim to be interim president is supported by around 50 nations – kicked off what he called "Operation Liberty", his plan to oust President Nicolas Maduro.
"Everyone to the streets, let's start the final phase of the end of the usurpation." he told supporters, speaking from the back of a pickup truck.
He called for a huge nationwide turnout on Wednesday, and urged his followers to redouble their efforts to maintain pressure in the streets.
"The greatest escalation of pressure we have seen in our history" has begun, Mr Guaido said.
The call comes amid massive blackouts and the collapse of water supplies affecting the nation, further exacerbated a growing political crisis.
The United States meanwhile has stiffened its economic sanctions against Mr Maduro, and one top US official warned Venezuela's military that it must protect the rights of peaceful protesters.
At the rally, Mr Guaido also warned Cuba's President Miguel Diaz-Canel that the supply of subsidised Venezuelan oil to the Caribbean communist island nation was over.
Venezuela has been sending cheap oil to Cuba in exchange for labour from Cuban doctors and teachers, but Mr Guaido said the oil was actually financing a Cuban intelligence group known as G2 that was cracking down on Maduro opponents in the Venezuelan military.
"The exploitation of Venezuelan oil is over, so Mr Diaz-Canel, Venezuelan oil will not be used to submit and investigate our military officials" through the G2, he told the crowd.
Pro-Guaido protests drew thousands in rallies across the country on Saturday.
A pro-Maduro counter-demonstration in Caracas, with supporters dressed in red, drew a large crowd that gathered at the Miraflores presidential palace.
"Together, permanently mobilised, let's keep defending national peace and independence; no more interference!" Mr Maduro tweeted.
Later, he called upon Mexico and Uruguay to relaunch their proposal for dialogue to resolve the crisis without foreign intervention. The two countries had first introduced the idea in January.
Two opposition deputies were detained at an anti-government demo in the western city of Maracaibo, but a few hours later Guaido announced that the two had been released.
Elimar Diaz, a lawmaker who marched in Maracaibo, said the protest there had encountered "brutal repression", including tear gas canisters dropped from helicopters, the use of National Guard armoured vehicles and attacks by members of the pro-government militia, known as "colectivos".
Mr Diaz said people in Maracaibo had gone "days without electricity" amid "inhumane rationing" by the government.
Mr Maduro has blamed US-backed sabotage for the massive blackouts that have deprived millions of power. The opposition blames a failure to maintain critical infrastructure.
Facing intense pressure at home and abroad, the Maduro government has sought to weaken Mr Guaido.
The government has stripped his parliamentary immunity, authorised his prosecution for proclaiming himself acting president, and banned him from holding public office for 15 years.
Mr Guaido said earlier this week he feared that he could be abducted by government agents.
Speaking to the pro-government Constitutional Assembly, Mr Maduro's top lieutenant Diosdado Cabello slammed the US point man on Venezuela, Elliott Abrams, as an "assassin".
"It is Abrams who should be in prison, condemned in the United States for genocide in Central America," said Lt Cabello, referring to the US official's controversial role in the Central American conflicts of the 1980s.
Washington meanwhile kept up the international pressure on Mr Maduro to step down.
Vice President Mike Pence on Friday announced fresh sanctions against 34 vessels belonging to Venezuela's state oil company and two companies that ship crude to Cuba.
"This is only a first step," US national security adviser John Bolton tweeted on Saturday in reference to the sanctions.
He cautioned the Venezuelan defense minister in a separate tweet of the official's "constitutional responsibility to protect innocent civilians who are peacefully demonstrating," adding: "Do not let the Cubans or the 'colectivos' inflict violence against Venezuelan patriots."
Mr Maduro is supported by the Venezuelan military, China and Russia.
Washington and its allies view the socialist president as illegitimate since he took office in January for a second term following elections widely seen as deeply flawed.
Washington has convened a UN Security Council for Wednesday to discuss the Venezuelan crisis.
Since Venezuela's massive blackout of March 7, the country has been subject to repeated power cuts, with electricity being rationed outside of Caracas.
The blackouts have knocked out water supplies as well as transport and communications, forcing many people to trim their work days to six hours.