A U.S.-flagged tanker heading for Bahrain was approached and threatened by Iranian gunboats in the Strait of Hormuz, a British maritime security firm says.

US officials say seizure of more tankers carrying Iranian oil is under consideration to pressure Tehran, but fears of retaliation and market disruption have so far kept Washington cautious.

Iranian gunboats unsuccessfully attempted to intercept a US oil tanker in the Strait of Hormuz on Tuesday before a US Navy vessel intervened, reports say.

Indian authorities have arrested and sanctioned three tankers linked to Iran in a crackdown on fuel smuggling. The Indian Coast Guard said that it had “busted an international oil-smuggling racket in a meticulously coordinated sea–air operation”. The three vessels were held about 100 miles west of Mumbai.

The United States has imposed sanctions on a fleet of nine ships accused of transporting hundreds of millions of dollars in forbidden Iranian oil to foreign markets.

DUBAI, Feb 3 (Reuters) - A group of Iranian gunboats approached a U.S.-flagged tanker in the Strait of Hormuz north of Oman, maritime sources and a security consultancy said on Tuesday. The Iranian boats ordered the tanker,