Violent street battles erupted in parts of Caracas on Tuesday in what was the most serious challenge yet to Maduro's rule - kicked off with a surprise video shot at dawn of Guaidó, flanked by several heavily-national guardsmen, urging a final push to topple Maduro.
Still, the surprise rebellion, dubbed "Operation Freedom," seemed to have garnered only limited military support.
Meanwhile, US National Security Adviser John Bolton said the Trump administration was waiting for three key officials, including Maduro's defence minister and head of the supreme court, to act on what he said were private pledges to remove Maduro. He did not provide details.
The dramatic events began early on Tuesday when Guaidó, flanked by a few dozen national guardsmen and some armoured crowd-control vehicles, released the three-minute video filmed near a Caracas air base.
In a surprise, Leopoldo Lopez, his political mentor and the nation's most-prominent opposition activist, stood alongside him. Detained in 2014 for leading a previous round of anti-government unrest. Lopez said he had been released from house arrest by security forces adhering to an order from Guaidó.
"I want to tell the Venezuelan people: This is the moment to take to the streets and accompany these patriotic soldiers," Lopez said.
As the two opposition leaders coordinated actions from vehicles parked on a highway overpass, troops loyal to Maduro sporadically fired tear gas from inside the adjacent Carlota air base.
A crowd that quickly swelled to a few thousand scurried for cover, reappearing later with Guaidó at a nearby plaza away from the disturbances. A smaller group of masked youths stayed behind on the highway, lobbing rocks and Molotov cocktails toward the air base, and setting a government bus on fire.
Amid the mayhem, several armoured utility vehicles careened over a berm and drove at full speed into the crowd. Two demonstrators, lying on the ground with their heads and legs bloodied, were rushed away on a motorcycle as the vehicles sped away dodging fireballs thrown by the demonstrators.
"It's now or never," said one of the young rebellious soldiers, his face covered in the blue bandanna worn by the few dozen insurgent soldiers
The head of a medical centre near where the street battles took place said doctors were treating 50 people, about half of them with injuries suffered from buckshot. At least one person had been shot with a firearm.
Amid the confusion, Maduro tried to project an image of strength, saying he had spoken to several regional military commanders who reaffirmed their loyalty.
"Nerves of steel!" he said in a message posted on Twitter.
Flanked by top military commanders, Defence Minister Vladimir Padrino López condemned Guaido's move as a "terrorist" act and "coup attempt" that was bound to fail like past uprisings.
"Those who try to take Miraflores with violence will be met with violence," he said on national television, referring to the presidential palace where hundreds of government supporters, some of them brandishing firearms, had gathered in response to a call to defend Maduro.
"Since 2002, we've seen the same pattern," Arreaza told The Associated Press, adding that most of Caracas was calm. "They call for violence, a coup, and send people into the streets so that there are confrontations and deaths. And then from the blood they try to construct a narrative."
Small groups of protesters threw up blockades of debris at several downtown intersections about 10 blocks from the presidential palace. But police in riot gear moved in quickly to clear the roads.
Most shops and businesses were closed and the streets of the capital unusually quiet, as people huddled at home to await the outcome of the day's drama.
Guaidó said he called for the uprising to restore Venezuela's constitutional order, broken when Maduro was sworn in earlier this year for a second term following elections boycotted by the opposition and considered illegitimate by dozens of countries.
For weeks, Guaidó had been promising a final push against Maduro, dubbed "Operation Freedom," to coincide with planned protests Wednesday.
But few observers gave it much chance of success as a stalemate emerged that left regular Venezuelans, already struggling from hyperinflation and blackouts, in the middle of a political battle between Guaidó and Maduro, who has managed to preserve the backing of his military as well as allies like Russia and Cuba.
Guaidó said that in the coming hours he would release a list of top commanders supporting the uprising. There were unconfirmed reports that General Manuel Christopher Figuera, who heads the feared intelligence agency responsible for keeping Lopez in state custody, was among members of the security forces who had decided to flip.
Anti-government demonstrators gathered in several other cities, although there were no reports that Guaidó's supporters had taken control of any military installations.
"The armed forces have taken the right decision," said Guaidó. "With the support of the Venezuelan people and the backing of our constitution they are on the right side of history."
As events unfolded, governments from around the world expressed support for Guaidó while reiterating calls to avoid violent confrontation.
Bolton rejected suggestions of a coup, and instead praised Guaidó for demonstrating immense bravery. He declined to discuss possible actions - military or otherwise - but reiterated that "all options" are on the table as President Donald Trump monitors developments "minute by minute."
He said he was waiting for key power brokers including Padrino, Supreme Court chief justice Maikel Moreno and head of the presidential guard to make good on their commitments to achieve the peaceful transfer of power to Guiado.
"All agreed that Maduro had to go. They need to be able to act this afternoon, or this evening, to help bring other military forces to the side of the interim president," Bolton said.
Elsewhere, Spain's socialist caretaker government urged restraint, while the governments of Cuba and Bolivia reiterated their support for Maduro.
