WASHINGTON (AFP) - The United States threatened new sanctions against the Venezuelan regime on Monday (May 21), following an opposition-boycotted election that Washington denounced as a "sham" and "illegitimate".

Secretary of State Mike Pompeo vowed "swift economic and diplomatic actions" following elections that kept Mr Nicolas Maduro in power and which observers described as deeply flawed.

US Vice-President Mike Pence said the election was "a sham - neither free nor fair. The illegitimate result of this fake process is a further blow to the proud democratic tradition of Venezuela."

The White House is expected to announce sanctions to "support the restoration" of Venezuelan democracy later on Monday.

"The United States will not sit idly by as Venezuela crumbles and the misery of their brave people continues," said Mr Pence.

Venezuela is already deep in the worst economic crisis of its history, with its people enduring food and medicine shortages that have sparked violent unrest and a mass exodus by hundreds of thousands of people.

Election officials said Mr Maduro won 68 per cent of the votes cast in Sunday's (May 20) presidential poll, far ahead of the 21 per cent won by his nearest rival, ex-army officer Henri Falcon.

But the vote was marred by a 52 per cent abstention rate - a historic high - following a boycott called by the Democratic Unity Roundtable (MUD) opposition coalition, which slammed the ballot as a "farce". Even before it took place, the US, Canada, the European Union and a dozen Latin American countries said they would not recognize the results.

"Until the Maduro regime restores a democratic path in Venezuela through free, fair, and transparent elections, the government faces isolation from the international community," Mr Pompeo said.