US forces struck five Iranian tankers in response to Tehran twice targeting an American warship over the past two days, US Central Command (Centcom) has said.
The US attacked oil tankers linked to Iran's Revolutionary Guards Corps (IRGC) in the Gulf of Oman, as well as a tanker near Kharg Island, a major oil terminal off Iran's Gulf coast, Centcom said on Tuesday night.
Iran retaliated by launching missiles at a US base in Jordan, though Jordan later said that it had shot down 18 of the 20 missiles with its air defence systems.
Tit-for-tat strikes between the two countries have escalated over the past week, more than six months after the US and Israel launched attacks on Iran.
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.
According to Centcom, Iran targeted a US Navy warship with ballistic missiles, which the US "successfully evaded". No American troops were harmed, it said.
Following the US retaliatory attack, Tehran also warned of further 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.
Centcom has claimed 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 comes through the island, transported through pipes from the mainland.