Updated at 2:30 p.m. ET
Juan Guaidó, Venezuela's most powerful opposition leader, has declared a start to the "final phase" of the effort to oust President Nicolás Maduro, urging supporters into the streets Tuesday and telling them, "The moment is now!"
The call for an uprising set off a cascade of demonstrations in Caracas, increasing clashes and raising the chances that members of Venezuela's military may face off against one another, depending on where their loyalties lie.
Early Tuesday morning, Guaidó released a three-minute video from an air base in eastern Caracas known as La Carlota, in which he described the Venezuelan people's fight. Flanked by men with helmets and weapons, he discussed ending the "usurpation," a term he has often used to describe Maduro's hold on the once-oil-rich nation.
López said he had been released by members of the military and Guaidó. "I'm at the La Carlota Base," he tweeted. "All to mobilize. It's time to conquer freedom."
Guaidó told reporters that high-ranking military officers have switched their allegiances to him.
"There are generals, there are lieutenant colonels, there are majors, there are colonels — it's a reflection of the country," he said, with Venezuela's flag blowing in the wind behind him.
The opposition figures' messages quickly raised tensions with Maduro's government, as demonstrators took to the streets of the capital to support members of the military who joined Guaidó. Some later gathered near the air base in a show of support.
Videos from the scene show people running and jumping into vehicles, with military helicopters and motorcycles nearby.
Motorcycle units from Venezuela's National Guard, who are loyal to Maduro, arrived at the base and closed its gates. People appeared to tear at the gates and crawl through an opening before being chased away.
Journalists on the ground report hearing the echo of gunfire and tear gas canisters being fired down streets, as well as seeing Molotov cocktails. At the scene of a large protest on a highway, one video segment from TV station T13 shows what appears to be a National Guard armored vehicle driving into a crowd of people.
The U.S. Embassy in Caracas is warning U.S. citizens to avoid the public demonstrations and to consider sheltering in place.
It's unclear how many members of the military may be siding with Guaidó and whether he received any assistance from the United States.
To avoid confusion amid the chaos that was unleashed Tuesday, armed men loyal to Guaidó in the Altamira neighborhood are using bracelets and blue scarves to identify themselves, a local journalist said.
Venezuelan Information Minister Jorge Rodríguez rejected news of a "coup attempt" in his country, saying on Twitter that the government is "deactivating a small number of traitorous military personnel."
Guaidó declared himself Venezuela's interim president in January, after being sworn in to lead the National Assembly. He has been recognized as the country's interim president by the United States and dozens of other nations.
Maduro has refused to step down from office. And on Tuesday, he issued a stream of tweets including one that invoked "Nerves of steel!" and insisted that forces remain loyal to him.
The chaos comes a day before Labor Day, meaning the clashes might continue when most Venezuelans will have the day off from work Wednesday.
"This is only the beginning," Carlos Vecchio, Guaidó's envoy to the U.S., said at a news conference. Meanwhile, protesters in support of and against the Maduro government gathered outside Venezuela's embassy in Washington and other capitals Tuesday.
Guaidó's boldest move yet against Maduro quickly prompted leaders in Washington to show their support.
Secretary of State Mike Pompeo welcomed the start of "Operación Libertad" on Twitter. "The U.S. Government fully supports the Venezuelan people in their quest for freedom and democracy. Democracy cannot be defeated," he said.
Sen. Marco Rubio, R-Fla., tweeted, "This is the moment for those military officers in #Venezuela to fulfill their constitutional oath & defend the legitimate interim President."
Rubio posted a video of a "showdown" on a highway. He said Maduro called for armed groups to go to the streets; the senator also said Chinese technicians have helped the Maduro regime take down social media communications.
Venezuela's telecommunications agency ordered Radio Caracas Radio to stop broadcasting after decades of continuous airtime. In response, the station announced it would turn to YouTube and Periscope, adding, "Nos escuchamos en libertad!" — "We hear each other in freedom!"
U.S. national security adviser John Bolton told Defense Minister Vladimir Padrino López that Venezuela's armed forces "must protect the Constitution and the Venezuelan people."
Vice President Pence told Guaidó and his supporters, "Estamos con ustedes! We are with you!"
President Trump has been briefed on the developments, White House spokesperson Sarah Sanders told reporters.
Luis Almagro, general secretary of the Organization of American States, welcomed the military members who joined Guaidó, saying "the fullest support" was necessary for a peaceful democratic transition.
Countries who support Maduro, including Cuba, are denouncing the opposition's calls for an uprising. Russia's Ministry of Foreign Affairs said Guaidó and his allies were trying to incite chaos in the public and clashes with armed forces. Russian President Vladimir Putin "paid much attention to the situation" in Venezuela during a meeting with his national security council, according to Kremlin spokesman Dmitry Peskov.
Maduro began his first presidential term in 2013 and was reelected in January amid allegations of fraud. Under the socialist government, Venezuelans have suffered from shortages of food, medicine and electricity as inflation has soared.
"I want a free Venezuela," a pregnant woman in a wheelchair told a local news outlet. She said she wanted her child to be born in freedom. "I'm tired of this, that's enough. It's not fair that we live like this."
This is a developing story. Details may change as more information becomes available.