The US state department has urged its citizens to “strongly consider” leaving Venezuela and ordered out non-emergency government staff as the head of the country’s armed forces warned of a civil war sparked by a US-backed “criminal plan” to unseat Nicolás Maduro.

In a live address to the nation on Thursday, the defence minister, Vladimir Padrino, accused the Venezuelan opposition led by Juan Guaidó, the United States and regional allies such as Brazil of launching an attempted coup against Maduro that risked bringing “chaos and anarchy” to the country.

“We are here to avoid, at all costs … a conflict between Venezuelans. It is not civil war, a war between brothers that will solve the problems of Venezuela. It is dialogue,” said Padrino.

In a significant blow to Venezuela’s newly energized opposition, the defence minister declared unwavering support for “our commander-in-chief, the citizen Nicolás Maduro”.

“We members of the armed forces know well the consequences [of war], just from looking at the history of humanity, of the last century, when millions and millions of human beings lost their lives,” Padrino added, flanked by the top brass of Venezuela’s armed forces.

Further bolstering Maduro’s position, the Russian president, Vladimir Putin, spoke to the Venezuelan leader by telephone and issued his first comments on the crisis, which he insisted was “provoked from abroad”, according to a Kremlin statement.

Addressing the supreme court in Caracas on Thursday afternoon, Maduro said he had told Putin “a great provocation is under way in Venezuela, directly by the US empire”.

“I believe the world is in no doubt: Donald Trump wants to impose de facto, unconstitutional government and carry out a coup in Venezuela against the people and against democracy … They want to dismember the republic.”

“Do we want a coup in Venezuela? Will we legitimise a puppet government imposed from abroad? Will we allow our constitution to be violated? No!” Maduro said.

Trump has warned that “all options are on the table” for a US response if the Maduro government seeks to hold on to power by force. His national security adviser, John Bolton, refused to exclude military action on Thursday, but said the immediate emphasis would be on economic measures.

“What we’re focusing on today is disconnecting the illegitimate Maduro regime from the source of its revenues,” Bolton told reporters. “We think consistent with our recognition of Juan Guaidó as the constitutional interim president of Venezuela that those revenues should go to the legitimate government. It’s very complicated. We’re looking at a lot of different things we have to do, but that’s in the process.”

He said that Washington was currently trying to strengthen the coalition against Maduro among American and European states. The EU has called for new elections but most member states have not followed Washington in recognising Guaidó, the head of the opposition-led national assembly.

The UK however, broke European ranks on Thursday and sided with the US.

“This regime has done untold damage to the people of Venezuela, 10% of the population have left Venezuela such is the misery they are suffering,” the foreign secretary, Jeremy Hunt, said in a statement issued in Washington before a meeting with the US secretary of state, Mike Pompeo, and Vice-President Mike Pence.

“So the United Kingdom believes Juan Guaidó is the right person to take Venezuela forward. We are supporting the US, Canada, Brazil and Argentina to make that happen.”

The statement stopped just short of echoing US language on recognising Guaidó, however. “It is UK policy to recognise states, not governments,” a British official said.

The US initially ignored the Maduro government’s order expelling embassy staff, but late on Thursday the state department announced it was withdrawing “non-emergency US government employees”.

“We are prepared to do the things we need to do to make sure we keep our people safe,” a state department spokesperson said. “The full range of United States government resources are at the ready to ensure the safety and security of US diplomats and their families.”

The US has called for a UN security council emergency session on Saturday to discuss the crisis in Venezuela, although Russia opposes a debate on what Moscow says is an internal Venezuelan matter.

A Venezuelan monitoring group claimed at least a dozen people had been killed in the unrest.

In his speech, Padrino described Juan Guaidó’s decision to declare himself Venezuela’s president on Wednesday as a shameful and laughable fact but one that risked unleashing a wave of bloodshed. “I have to alert the people of Venezuela to the severe danger that this represents to our integrity and our national sovereignty.”

Facing “a criminal plan that flagrantly threatens the sovereignty and independence of the nation”, Padrino said the armed forces would remain loyal to Maduro. Dissent would not be tolerated, he added ominously.

“We will not tolerate acts of vandalism or terrorism by groups that promote violence as a perverse mechanism to achieve their objectives,” he said before ending his address with the rallying cry “Chávez vive y la patria sigue!” (“Chávez lives and the homeland goes on!”).

Analysts have long held that Maduro’s survival depends on the backing of the military, who he has rewarded with senior positions in government and the state oil company PDVSA.

But it is unclear how solid that support is. Guaidó and the opposition-held national assembly have sought to peel away the military, offering an amnesty to members of the armed forces who help bring about what they term a return to democracy. This week, authorities arrested 27 national guardsmenwho tried to launch an uprising against Maduro.

Venezuela expert Miguel Tinker Salas said he believed one of the key objectives of Guaidó and his international backers was to find and exploit “fissures within the military” in order to unseat Maduro.

“What they were hoping, I suspect, was lower-ranking officers to show discontent or to show a break with their superiors. I don’t see any evidence of that so far,” beyond a small uprising in Caracas on Monday.

“So far the upper military class – the generals and the senior officers – have shown support for Maduro.”

Salas, the author of Venezuela: What Everyone Needs to Know, said he was troubled by the potential for bloodshed in the days and weeks ahead.

“The risk is that this escalates into an open confrontation [between pro- and anti-Maduro groups] and then you have a foreign intervention,” he said.

“That is something that would be not only dangerous but catastrophic for Venezuela. And for Latin America it would be a return to the 1980s Reagan era of civil wars and conflicts that proved devastating to El Salvador, Honduras and Guatemala and those countries of the region. We had hoped to be beyond that.”