Venezuelan opposition leader Juan Guaidó said Tuesday he was launching a military-backed operation to oust President Nicol á s Maduro.

s Maduro. He gathered with supporters in Caracas, the Venezuelan capital, where a firefight broke out between his supporters and pro-regime forces loyal to Maduro.

Guaidó says he has the support of the military, which has historically backed Maduro. The extent of that support for Guaidó is unclear, but some reports indicate it may not be as strong as stated.

Guaidó has been locked in a heated power struggle with Maduro since he declared himself the legitimate interim president in January.

The US, the UK, and other international partners have offered their support for Guaidó, whom they recognize as Venezuela's leader. Maduro, however, has the support of the Cubans and the Russians.

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Venezuelan opposition leader Juan Guaidó launched an operation against the Venezuelan government led by President Nicolás Maduro on Tuesday morning, sparking a confrontation that has evolved into an escalating armed conflict.

In a message to supporters online, Guaidó announced the beginning of what he called "Operation Liberty," calling for supporters to rally at a military air base in the Venezuelan capital of Caracas.

Supporter gathered at the La Carlota military air base, where they reportedly came under fire, igniting a gun battle between pro-regime and opposition forces. Reuters said both sides appeared to be using live rounds.

Part of the clash can be seen in video footage from Latin American TV channel NTN24. Apparent gunfire can be heard in the video.

Shocking videos have surfaced online showing a military vehicle ramming opposition protesters. Sen. Marco Rubio tweeted about the images: "Military & security leaders must realize they are & will be held responsible for this."

A separate video posted to social media shows protestors throwing rocks and sticks at the military vehicles moments before one of them swerved into the crowd.

Guaidó also rallied supporters at Francia de Altamira square, where he told supporters, "Today it became clear that the armed forces are with the people and not with the dictator."

In response, Maduro rallied his own supporters and in a tweet called for "nerves of steel." He wrote that his military commanders remain loyal to him.

The movement to oust Maduro, while having civilian support, appears to be struggling to gain support from the military. Reports from inside Venezuela suggest that the operation was planned for another day and had military support, but as Guaidó's arrest appeared imminent, action was taken sooner than expected. The military reportedly backed out.

In a press briefing Tuesday afternoon, White House National Security Advisor John Bolton called out certain military leaders by name, reminding them that they pledged to support Guaidó. On Twitter, he warned other Venezuelan officials that they must abandon Maduro or risk being taken down with him.

Bolton has said that "all options are on the table" when it comes to possible US responses to the situation in Venezuela.

Nations around the world — including the US, most Latin American countries, and most European countries — recognize Guaidó's claim to be the rightful leader of Venezuela.

A spokesman for the Venezuelan government said it was taking action against "a small group of traitors" in the military who had defected to Guaidó. The Venezuelan foreign minister has announced that Maduro "is in his place of command as always, and he is in control of the situation," Reuters reported.

In his announcement Tuesday morning, Guaidó was seen surrounded by uniformed men whom he described as Venezuelan soldiers loyal to him.

"People of Venezuela, the end of the usurpation has begun," Guaidó said on Twitter. "At the moment I am meeting with the principal military units from the armed forces to start the final phase of Operation Liberty."

He said that the events of the day will set in motion the "definitive end" to Maduro's rule, which began in 2013 after the death of longtime Venezuelan president Hugo Chávez.

Guaidó was joined by Leopoldo López, another opposition leader who has spent the past two years under house arrest for two years. López tweeted that he was freed by soldiers supporting Guaidó.

Venezuela's government said it was working to stop the uprising.

Jorge Rodríguez, the Vice President of Communications, wrote on Twitter that the state was "confronting and deactivating a small group of traitors in our military personnel."

Venezuela's defense minister, Vladimir Padrino, tweeted: "The armed forces are firmly in defense of the national constitution and its legitimate authorities."

Soldiers supporting Guaidó. (Ariana Cubillos/AP)

Diosdado Cabello, the leader of Maduro's socialist party, urged Maduro supporters to rally in front of the presidential palace, according to the Associated Press. Hundreds gathered at Miraflores Palace, and chanted slogans of support.

Guaidó has been trying to oust Maduro since January, when Guaidó declared himself the legitimate interim president of Venezuela. He cited emergency powers in the constitution that he argued gave him the right to rule.

You can click here for Business Insider's timeline of the political crisis in Venezuela.

More than 50 countries, including the US, the UK, and all the nations of the European Union, have backed Guaidó's claim to power.

Most Latin American nations also support Guaidó, as shown in this map:

The countries in green recognized Guaidó as Venezuela's interim president as of January 24. Countries in red supported Maduro, while Venezuela itself is in yellow. (amCharts/INSIDER)

Senior figures in the US government voiced support for Guaidó as news of Operation Liberty spread.

US Vice-President Mike Pence posted a message on Twitter, directly addressing Guaidó and his supporters. It said: "America will stand with you until freedom & democracy are restored."

—Vice President Mike Pence (@VP) April 30, 2019

US Secretary of State Mike Pompeo tweeted that the US government "fully supports the Venezuelan people in their quest for freedom and democracy."

Acting Secretary of Defense Patrick Shanahan also voiced his support.

—Acting SecDef Pat Shanahan (@ActingSecDef) April 30, 2019

The White House said that President Donald Trump is being briefed on the situation, and US Southern Command is monitoring the situation.

"We are monitoring the recent developments in Venezuela closely and are in close contact with our interagency partners and senior chain of command. At the present time, U.S. Southern Command's mission remains unchanged," Col. Armando Hernandez, a SOUTHCOM spokesman told Reuters.

A spokesman for UK Prime Minister Theresa May told reporters on Tuesday: "The UK, along with its international partners, recognises Juan Guaidó as the interim president.

"Our focus is on a peaceful resolution to the crisis and the restoration of Venezuelan democracy," he said, concluding that "the Maduro regime must end."