Vice president Mike Pence said four Venezuelan state governors allied to Mr Maduro were the target of the new sanctions, while he urged the international community to freeze assets of the nation's state-run oil company. The US also asked the United Nations Security Council to hold an urgent meeting on the crisis.

“I want to assure you, President Guaidó, that the tragic events of the past weekend have only steeled the resolve of the United States of America,” Mr Pence said at a meeting of the Lima Group in Colombia.

The meeting was attended by opposition leader Juan Guaido, who last month declared himself Venezuela's president.

According to the Associated Press, Mr Pence added. “We are with you 100 per cent.”

Also in Colombia at the weekend, where he visited efforts to transport US aid across the border into Venezuela – an effort that resulted in violence and several deaths – was Republican senator Marco Rubio, who has been highly influential on Donald Trump’s Latin American policy and whom the New York Times has termed the “ouster in chief”.

Venezuela aid protests: Civilians demand food and medicine Show all 5 1 /5 Venezuela aid protests: Civilians demand food and medicine Venezuela aid protests: Civilians demand food and medicine Demonstrators push a bus that was torched during clashes with the Bolivarian National Guard AP Venezuela aid protests: Civilians demand food and medicine Demonstrators are seen through the cracked windshield of a torched bus AP Venezuela aid protests: Civilians demand food and medicine A woman moves away from the flames of a burning bus AP Venezuela aid protests: Civilians demand food and medicine A bus that was torched during clashes with the Bolivarian National Guard AP Venezuela aid protests: Civilians demand food and medicine Demonstrators push away a bus that was torched during clashes AP

On Sunday, he tweeted several messages attacking Mr Maduro’s government before then posting three images of ousted dictators – Libya’s Gaddafi, Panama’s Manuel Noriega and Romania’s Nicolae Ceausescu. The gruesome, blood-laced image of the Libyan leader was taken as he was bayoneted to death by rebels in the city of Sirte in October 2011. Nato had earlier engaged in a devastating bombing campaign against Gadafi's forces.

Mr Rubio’s tweet of the image contained no text, but quickly sparked outcry on social media. A number of commentators said he was tweeting the equivalent of stills from a “snuff movie”.

In Colombia at the meeting of nations from the Americas, Mr Pence spoke with Mr Guaido, who Washington had encouraged to declare himself the country’s “legitimate” president and who it quickly regonised as such after he did so. The UK, Canada and up to 50 other nations quickly followed, while China, Russia and Mexico still recognise Mr Maduo.

Mr Pence accused Mr Maduro’s forces of burning several trucks containing medical supplies over the weekend as the opposition tried to deliver US aid, even though it was unclear how they were set alight.

“As the world watched, the tyrant in Caracas danced as his henchmen murdered civilians and burned truckloads of food and medicine destined for the people of Venezuela,” Mr Pence claimed. “These men worked to block aid for people in need and suppress peaceful protests – and their actions will not go unpunished.

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“In the days ahead, the US will announce even stronger sanctions on the regime's corrupt financial networks. We will find every last dollar they have stolen and return that money to the Venezuelan people.

“As we continue to bring economic and diplomatic pressure to bear on the Maduro regime, we hope for a peaceful transition to democracy, but as President Trump has made clear, all options are on the table.”

But others - including several European nations - voiced caution. Hamilton Mourão, vice president of Brazil, one of the nations that has recegnised Mr Guaido, said under no circumstances would his country allow the US to intervene militarily in Venezuela from Brazilian territory.

Mr Maduro has denied claims that he is refusing to accept aid. Indeed, the UN has stepped up distribution of humanitarian supplies in the country. His supporters point out the US has previously used shipments of aid in Latin America to smuggle weapons to rebels. Three decades ago, Elliott Abrams, currently Mr Trump’s point person on Venezuela, oversaw such an operation against the democratically elected government of Nicaragua.

Mr Maduro on Monday tweeted that the “empire and its lackey” must understand that in “Venezuela the self-determination of our people reigns. We will solve the problems in a national union, with the Bolivarian government that I preside over. Together for Venezuela!”.