The four fuel cargo vessels — Luna, Pandi, Bering and Bella — have been seized in the open sea for the first time in recent days for breaching the sanctions imposed by US President Donald Trump, and are currently on their way to Houston, US officials said.

In July, US authorities filed a complaint to seize fuel on four tankers that Iran was planning to send to Venezuela to block proceeds from oil sales to Iran.

Iran's economy, historically dependent on oil exports, has dried up in recent years, with the US government reinstating crippling economic sanctions.

The tensions between Iran and the US intensified after Trump declared a unilateral withdrawal from the 2015 Iran nuclear agreement in May 2018 and reintroduced sanctions that had been relaxed by his predecessor.

The sanctions have struck Iran's oil sector hard, with many countries slashing oil imports from Iran, expecting a retaliation from the US.

Maritime Business World