The United States launches massive strikes against Iran, which retaliates in two Gulf countries.

The United States struck more than 80 targets in Iran in response to Iranian attacks on commercial vessels in the Strait of Hormuz, prompting retaliation from Tehran on Wednesday, which said it had attacked US bases in Kuwait and Bahrain.

Washington also reinstated its economic sanctions on Iranian oil following the attacks on ships. Both sides accuse each other of violating their memorandum of understanding, signed on June 17 to end the war that began on February 28 with the US-Israeli offensive against the Islamic Republic.

This text notably provides for the reopening of the Strait of Hormuz - through which normally 20% of the world's crude oil and liquefied gas (LNG) pass and whose closure by Tehran had shaken the world economy and caused prices to soar - as well as the lifting of American sanctions on Iranian oil.

Three ships were attacked in the Strait of Hormuz within 24 hours, the British maritime security agency UKMTO reported on Tuesday. Qatar and Saudi Arabia blamed Iran for two of the attacks.

Denouncing "Iranian attacks" and a "flagrant violation of the ceasefire," the US military launched a series of "powerful strikes" against Iran, claiming to have hit "more than 80 targets," including "Iranian air defense systems," the US military command for the Middle East (Centcom) detailed in a statement.

- "Decisive measures" from Tehran -

Iran, where media reported explosions on Tuesday at sites near the Strait of Hormuz, immediately warned the United States against this "violation" of the memorandum of understanding, warning that it would "take decisive measures to protect its interests and national security," in a statement from its Ministry of Foreign Affairs.

A few hours later on Wednesday, Iran's Revolutionary Guards announced they had struck 85 facilities at US military bases in Kuwait and Bahrain, according to state television.

"In a first response" to the American strikes, "the Navy and the Aerospace Force of the Islamic Revolutionary Guard Corps (IRGC) conducted a joint operation using missiles and drones, striking 85 strategic American military installations" and shooting down an MQ-9 drone, according to a statement broadcast by the official television Irib.

Air raid sirens sounded in Bahrain, the Gulf state's Interior Ministry announced, without providing further details. The Kuwaiti military also indicated on Wednesday that it was responding to drone and missile attacks, without specifying their origin.

- Rise in oil prices -

"Iran's actions in the strait are totally unacceptable to the United States and will not go unpunished," a US government official said on condition of anonymity, after the Treasury Department published a document banning "new transactions" of Iranian hydrocarbons starting Tuesday.

In this context of tensions, the price of a barrel of US WTI oil rose by 2.63% to $72.29 at the opening of Asian markets.

Navigation had resumed in the Strait of Hormuz following the signing of the memorandum of understanding, despite some incidents.

In late June, accusing Iran of targeting two ships, the United States bombed the country, which retaliated by targeting its Gulf neighbors, Kuwait and Bahrain. Washington and Tehran subsequently agreed to cease hostilities.

Saudi Arabia on Tuesday condemned "the targeting by the Islamic Republic of Iran of the Saudi oil tanker Wedyan" which was transiting the Strait of Hormuz, as well as that of "the Qatari LNG carrier Al-Rakayyat", denouncing "an attack on the security of international navigation and the security of global energy supplies".

According to Centcom, the targeted ships are the Al-Rakayyat flying the Marshall Islands flag, the Wedyan flying the Saudi flag, and the Cyprus Prosperity flying the Liberian flag.

Qatar had announced that it had summoned the Iranian chargé d'affaires, demanding "explanations about this attack"; Iranian Foreign Ministry spokesman Esmail Baghai denounced an "unacceptable" accusation from Qatar.

Without attributing them, the UKMTO agency also reported two other incidents on Tuesday: an oil tanker hit by an unidentified projectile, suffering "structural damage", and a tanker struck by a drone of unknown origin.

Iran, despite US opposition, rules out any return to the pre-war situation, when passage through the strait was free, and threatens ships tempted to bypass the only route it has authorized along its coasts.

This rise in tensions comes as Iran has been holding a six-day national funeral since Saturday for its supreme leader, Ali Khamenei, who was killed on the first day of the war by Israeli-American strikes, and whose body has just arrived in Iraq for processions in Najaf and Karbala, two cities housing the most revered shrines of Shiite Muslims.