US naval forces have intercepted and turned back several oil tankers linked to Iran following the enforcement of a blockade of the Strait of Hormuz, in a move aimed at tightening economic pressure on Tehran.

According to officials cited by The Wall Street Journal, US forces have ordered at least eight vessels heading to or from Iranian ports to reverse course since Monday.

In each case, naval units contacted the crews via radio and instructed them to turn back, with all ships complying without the need for boarding.

The blockade is being enforced from the Gulf of Oman, a critical transit zone for ships passing through the Strait of Hormuz into open waters.

A US official told The Associated Press that this positioning allows American forces to monitor vessels departing Iranian ports before intercepting those subject to restrictions.

US Central Command said that no ships successfully passed the blockade in its first 24 hours, adding that several merchant vessels had already complied with orders to turn back into Iranian waters.

Tankers approaching the strait reportedly reversed course soon after the restrictions took effect, although at least one vessel initially turned around before later proceeding through the waterway.

The measures are intended to curb Iran’s oil exports, which have continued despite sanctions, often through so-called “dark” shipping practices designed to evade detection.

These exports — largely destined for Asian markets —have been a key source of revenue for Tehran since the conflict began.