US forces struck five Iranian tankers in response to Tehran twice targeting an American warship over the past two days, US Central Command (Centcom) said.
Four Iranian oil tankers linked to Iran's Revolutionary Guards Corps (IRGC) in the Gulf of Oman were targeted, as well as another tanker near Kharg Island, a major oil off Iran's Gulf Coast, Centcom added.
Tehran retaliated by launching missiles at a US base in Jordan, though Jordan later said that it had shot down 18 of the 20 Iranian missiles with its air defence systems.
Tit-for-tat strikes between the two countries have escalated in the past week, more than six months after the US and Israel launched attacks on Iran on 28 February.
Oil prices rose in early trading in Asia. Benchmark Brent crude was up by 1.5% at $99.41 (£73.39) a barrel, while US-traded oil was 1.6% higher at $94.55.
Iran has warned of further retaliatory strikes on US ships in Kuwaiti and Bahraini ports.
The IRGC Navy Command warned all oil tanker crews near Kuwaiti and Bahraini ports linked to the US to "immediately leave their vessels whether at anchor or at the ports because they will be targeted".
Two of the missiles fired by Iran towards Jordan fell in unpopulated areas, an official spokesperson for the Jordanian Armed Forces said.
The latest round of escalation comes after Iran targeted a US Navy warship with ballistic missiles, which the US "successfully evaded", according to Centcom. It added that no American troops were harmed during the attacks.
In response, the US said that the five Iranian oil tankers it targeted were "part of a multi-billion-dollar shadow network that funds the IRGC and its regional proxies".
Kharg Island - where one Iranian tanker was attacked in the latest round of strikes - hosts Iran's main terminal for exporting oil.
Some 90% of the country's crude oil passes through the island, transported through pipes from the mainland.
When asked by reporters about the latest tit-for-tat strikes between the US and Iran, US Secretary of State Marco Rubio said the situation was "pretty straightforward".
"Iran continues to try to hit US naval ships. And, for every time they do that or try to do that, they're going to lose tankers. And I think you'll see that again today," Rubio told reporters during a trip in Colombia.
On 5 September, the US struck three Iranian oil tankers after Tehran attempted to attack a US aircraft carrier and guided missile destroyer.
The latest escalation in fighting flared last week, following a month of relative calm.
Source: BBC
– Agencies
