A tanker docked in Venezuela [AFP Yonhap News]

The United States, which has been blocking Venezuela's crude oil exports, has now seized a fifth oil tanker.

Citing U.S. government officials, the Wall Street Journal (WSJ) reported on the 9th (local time) that the U.S. Coast Guard boarded the oil tanker 'Olina'.

Reuters also reported that the U.S. had seized the Olina in the Caribbean Sea near Trinidad.

This oil tanker, originally named 'Minerva M', was placed on the U.S. sanctions list in January last year for its involvement in transporting Russian crude oil.

The Olina flew the flag of East Timor, but this was not its genuine registration, Reuters reported. Vessels that falsify their registration to evade sanctions, like the Olina, are known as the so-called 'shadow fleet'.

An industry source told Reuters that the Olina had departed from Venezuela last week laden with crude oil after the U.S. arrested Venezuelan President Nicolás Maduro, but was returning after the U.S. blockade.

The U.S. has been deploying warships in the vicinity to block crude oil exports and cut off Venezuela's funding. This is the fifth time the U.S. has seized an oil tanker citing sanctions violations.

The seizure of the oil tanker also serves as a warning to Russia, China, and Iran, which have been trading oil with Venezuela.