US President Donald Trump has said he is ordering a "a total and complete" blockade of all sanctioned oil tankers going into and out of Venezuela.

In a post on Truth Social, he said Venezuelan leader Nicolás Maduro's government had been designated a foreign terrorist organisation and accused it of stealing US assets, as well as "Terrorism, Drug Smuggling, and Human Trafficking".

"Therefore, today, I am ordering A TOTAL AND COMPLETE BLOCKADE OF ALL SANCTIONED OIL TANKERS going into, and out of, Venezuela," he added.

His remarks came a week after the US seized an oil tanker off the coast of Venezuela. In a statement, Venezuela's government said it rejected Trump's "grotesque threat".

In his post, Trump said Venezuela was "completely surrounded by the largest Armada ever assembled in the History of South America".

He added that it will "only get bigger" and "be like nothing they have ever seen before".

Trump also accused Maduro's government of using stolen oil to "finance themselves, Drug Terrorism, Human Trafficking, Murder, and Kidnapping".

The Trump administration has repeatedly accused Venezuela of drug smuggling, and since September the US military has killed at least 90 people in strikes on boats it alleged were carrying fentanyl and other illegal drugs to the US.

In recent months, the US has also moved warships into the region.

Venezuela - home to some of the world's largest proven oil reserves - has, in turn, accused Washington of seeking to steal its resources.

The US, under both Trump and former President Joe Biden, has opposed the Maduro government for years and pressed for him to be removed by instituting stringent sanctions.

Last week, the US imposed fresh sanctions on six more ships it said were carrying Venezuelan oil.

Sanctions were also placed on some of President Maduro's relatives and on businesses associated with what the US called his illegitimate regime.

A day earlier the US said it had seized a tanker off Venezuela's coast.

The White House said the seized vessel, called the Skipper, had been involved in "illicit oil shipping" and would be taken to an American port.

Venezuela's government denounced the seizure, with Maduro saying the US "kidnapped the crew" and "stole" the ship.

The US had built up its military presence in the Caribbean Sea, which borders Venezuela to the north, in the days before the raid.

It involved thousands of troops and USS Gerald Ford – the world's largest aircraft carrier– being positioned within striking distance of Venezuela.

Congressman Joaquin Castro, a Democrat representing Texas, said Trump's "naval blockade is unquestionably an act of war".

He added that US lawmakers will on Thursday vote on a resolution "directing the president to end hostilities with Venezuela".