There were explosions on the Front Altair and Kokuka Courageous and the crews were evacuated, according to reports. The UK Maritime Trade Operations, which is part of the Royal Navy, earlier warned of an unspecified incident and urged “extreme caution”. Meanwhile Iranian media claimed two oil tankers had been targeted in the area.
The US Navy’s Bahrain-based Fifth Fleet said their forces are assisting tankers after receiving two distress calls.
Joshua Frey of the Fifth Fleet said: “We are aware of the reported attack on tankers in the Gulf of Oman. US Naval Forces in the region received two separate distress calls at 6.12am local time and a second one at 7.00am.”
Iran has denied involvement, but it comes as Tehran-backed rebels in Yemen have also launched missile and drone attacks on Saudi Arabia.
And a similar attack took place a month ago in which four tankers were struck in the region.
The Gulf of Oman connects the Arabian Sea with the strategic Strait of Hormuz, which then runs to the Persian Gulf.
It borders Iran and Pakistan on the north, Oman on the south, and the United Arab Emirates on the west.
The incident comes as tensions are threatening to reach fever pitch between the US and Iran.
Japanese Prime Minister Shinzo Abe is currently visiting Iran in a bid to de-escalate the situation.
Speaking yesterday after talks with Iranian President Hassan Rouhani, Mr Abe warned that any “accidental conflict” must be avoided.
He is due to meet with Iran’s Supreme Leader Ayatollah Ali Khamenei today, for the second and final day of his visit.
Japan’s chief cabinet secretary Yoshihide Suga said that Mr Abe’s trip aimed to help ease tensions in the Middle East but not specifically between Tehran and Washington.
Iran is poised to break the 2015 nuclear deal which US President Donald Trump pulled out of last year, branding it “decaying and rotten”.