Trump backs Venezuelan opposition leader as President forcing Nicolas Maduro to cut ties with Washington

US President Donald Trump has officially recognised Venezuelan opposition leader Juan Guaido as the country's legitimate President, a move that forced the South American nation's incumbent leader Nicolas Maduro to cut "remaining" political and diplomatic ties with Washington.

Hours after Trump's announcement on Wednesday, a defiant Maduro appeared before supporters and accused the US of backing an attempted coup, reports CNN.

"We cannot accept the invasive policies of the empire, the US, the policies of Donald Trump," he said to cheers from the crowd.

"Venezuela is a land of liberators... We will not surrender."

Maduro also asked American diplomats in Venezuela to leave within 72 hours.

"The imperial government of the US is leading a coup attempt against us in order to install a puppet presidency that they can control in Venezuela," he added.

Maduro and Trump's announcements came after Guaido on Wednesday told a large crowd of supporters in Caracas that he was assuming the powers of Venezuela's executive branch and would fight against Maduro's "usurpation" of the presidency.

The governments of Argentina, Canada, Brazil, Colombia, Peru, Ecuador, Chile, Paraguay and Costa Rica have announced that they recognize Guaido as Venezuela's interim president.

European Council President Donald Tusk expressed support and called on other European countries to join him.

But Mexico said that it continues to recognise Maduro as President.

US Secretary of State Mike Pompeo also reiterated the US' support to Guaido, saying that Maduro does not have "the legal authority to break diplomatic relations with the US or to declare our diplomats persona non grata".

The US Embassy in Caracas issued a security alert indicating that diplomats and their families will be restricted to travel only within a few neighbourhoods in Caracas and school children will be staying at home.

The embassy will remain open during regular business hours but all visa appointments for Thursday have been cancelled, the alert said.

Guaido responded to Maduro's speech via Twitter, telling all diplomatic missions and accredited staff that Venezuela "wants you to maintain your diplomatic presence in our country".

"Any messages to the contrary lack any validity, since they come from people or entities that have been characterised as usurpers," he said in the statement.

"They have no legitimate authority to make any statements on this."

Sporadic clashes erupted after Guaido's announcement, with news footage showing National Guard members launching tear gas canisters at anti-government demonstrators near one of the main highways in the capital.