Venezuela's self-proclaimed acting president Juan Guaido claimed on Tuesday that troops had joined his campaign to oust President Nicolas Maduro, whose government vowed to put down what it called an attempted coup by the US-backed opposition leader.

An apparently carefully planned attempt by Guaido to demonstrate growing military support disintegrated into rioting as palls of black smoke rose over eastern Caracas.

The government said it was “deactivating” an attempted coup by a small group of “treacherous” soldiers. And there was little early sign Maduro's iron grip on the military — which has kept him in power in a months-long standoff with Guaido — had slipped.

Read: Venezuela’s military backs Maduro, accuses Guaido of ‘coup’

On Twitter, he claimed the military chiefs had assured him of their “total loyalty”.

Confusion reigned in Caracas as a crowd that swelled to thousands, many waving Venezuelan flags, flocked onto a highway near a Caracas military base.

Guaido had rallied his supporters with an early morning video message that showed him with armed troops he said had heeded months of urging to join his campaign to oust Maduro.

The 35-year-old National Assembly leader — recognized as interim president by more than 50 countries — was filmed outside the La Carlota air base, where he urged the armed forces inside to join him.

Guaido claimed the move was the “beginning of the end” of Maduro's regime, and there was “no turning back”. But as the crowd swelled around the base, police fired tear gas to keep them away from the perimeter.

Later troops in riot gear, backed by armored vehicles and water tankers, lined up against the demonstrators on a highway wreathed in tear-gas.

Several of the vehicles ran into the crowd, injuring some of the protesters. Rioters later blocked the highway with a bus and set it on fire.

A pall of black smoke also rose from an area near a helicopter hangar on the base. Soldiers put out the fire and fired tear gas at demonstrators who were trying to dismantle the steel perimeter fence.

“Today is the day Maduro resigns. Today is the day all the country's drug dealers resign. Today we have a Venezuela. Today we have a nation,” said one protester amid the confusion.

As UN Secretary General Antonio Guterres appealed to all sides to avoid violence, Venezuela's army chief and defense minister, General Vladimir Padrino, issued a stark warning of possible “bloodshed” — adding that he would hold the opposition responsible.

In a message on Twitter, Padrino said the situation in military barracks and bases in the country was “normal.” He later said an army colonel had received a bullet wound to the neck during the clashes in Caracas.

Communications Minister Jorge Rodriguez called on the army “to remain on maximum alert to — with our glorious National Bolivarian Armed Forces — defeat the attempted coup and preserve peace.”

US support

The US, meanwhile, threw its full support behind Guaido, with the White House calling on the military to protect the people and support the country's “legitimate institutions,” including the opposition-controlled National Assembly.

“The US Government fully supports the Venezuelan people in their quest for freedom and democracy. Democracy cannot be defeated,” US Secretary of State Mike Pompeo said on Twitter.

Russia, Maduro's main backer and creditor with China, accused Guaido of “fueling conflict” in the oil-rich country.

Maduro's leftist Latin American allies Cuba and Bolivia also condemned Guaido.

President Ivan Duque of neighboring Colombia — home to more than a million refugees from Maduro's regime — called on Twitter for “soldiers and the people of Venezuela to place themselves on the right side of history, rejecting dictatorship and Maduro's usurpation.”

Internet observatory NetBlocks reported “multiple internet services” were restricted in Venezuela following Guaido's appeal.

'Definitive phase'

In his video, recorded outside the La Carlota base, Guaido said the “definitive phase” had begun in his attempt to oust Maduro — who has presided over a catastrophic economic implosion since taking over from his late mentor Hugo Chavez in 2013.

“Brave soldiers, brave patriots, brave men supporting the constitution have answered our call,” Guaido said.

Guaido appeared alongside high-profile opposition politician Leopoldo Lopez who had been put under house arrest by Maduro's regime but who announced he had been “freed” by soldiers supporting Guaido.

Tuesday's call comes ahead of opposition plans to hold a massive Mayday protest in Caracas.

Tensions in Venezuela have been ratcheted up to a critical level this year, after Guaido, who is head of the opposition-ruled National Assembly, announced January 23 that he was the acting president under the constitution. He said Maduro had been fraudulently re-elected last year.

The United States and major Latin American powers including Brazil, Peru and Chile swiftly backed Guaido, followed later by EU nations.

Yet although US President Donald Trump has repeatedly said “all options” are on the table regarding Venezuela — including, implicitly, military action -- there has been no noticeable US military mobilization.

Instead, Washington has upped the economic pressure, through sanctions aimed at Maduro's regime and by cutting sales of Venezuelan oil -- the South American country's main revenue earner.

It also warned against any attempt to arrest Guaido, who has been left free to roam Venezuela and hold rallies.

Maduro and his government have repeatedly accused the United States of trying to foment a coup, and blame the economic devastation in the country on the tightening US sanctions.