The US Coast Guard is in "active pursuit" of another vessel in international waters near Venezuela as tensions in the region continue to escalate.

US authorities have already seized two oil tankers this month - one of them on Saturday.

Sunday's pursuit related to a "sanctioned dark fleet vessel that is part of Venezuela's illegal sanctions evasion", a US official said. "It is flying a false flag and under a judicial seizure order."

Washington has accused Venezuela of using oil money to fund drug-related crime, while Venezuela has described the tanker seizures as "theft and kidnapping".

US President Donald Trump last week ordered a "blockade" of sanctioned oil tankers entering and leaving the country.

Venezuela - home to the world largest proven oil reserves - has accused the Trump administration of trying to steal its resources.

US authorities have not yet officially confirmed Sunday's pursuit, and the exact location and name of the tanker involved is not yet known.

As of last week, more than 30 of the 80 ships in Venezuelan waters or approaching the country were under US sanctions, according to data compiled by TankerTrackers.com.

Saturday's seizure saw a Panamanian-flagged tanker boarded by a specialised tactical team in international waters.

That ship is not on the US Treasury's list of sanctioned vessels, but the US has said it was carrying "sanctioned PDVSA oil".

In the past five years, the ship also sailed under the flags of Greece and Liberia, according to records seen by BBC Verify.

"These acts will not go unpunished," the Venezuelan government said in response to Saturday's incident. It added that it intended to file a complaint with the United Nations Security Council and "other multilateral agencies and the governments of the world".

Venezuela is highly dependent on revenues from its oil exports to finance its government spending.

In recent weeks, the US has built up its military presence in the Caribbean Sea and has carried out deadly strikes on alleged Venezuelan drug-smuggling boats, killing around 100 people.

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

Secretary of State Marco Rubio told reporters on Friday: "It is clear that the current status quo with the Venezuelan regime is intolerable for the United States."

He added that the goal of the Trump administration is to change that dynamic.

His comments were criticised by Venezuela's foreign minister, who accused Rubio of dragging the US down the path of "regime changes".

It has provided no public evidence that these vessels were carrying drugs, and the military has come under increasing scrutiny from Congress over the strikes.

The Trump administration has accused Venezuelan President Nicolás Maduro of leading a designated-terrorist organisation called Cartel de los Soles, which he denies.