TEHRAN: A crucial region for the global oil trade, the Gulf has been the theatre of escalating tensions since the unilateral withdrawal of the United States in May 2018 from the nuclear deal between Iran and world powers and its renewal of biting sanctions against Tehran.

- Withdrawal from the nuclear deal -

On May 8, 2018, US President Donald Trump announces the US withdrawal from the international agreement on Iran's nuclear power and the reinstatement of economic sanctions against Iran.

Finalised in Vienna in 2015 between Iran and the P5+1 (the five permanent members of the UN Security Council -- China, Britain, France, Russia and the US -- plus Germany), the Joint Comprehensive Plan of Action (JCPOA) lifted some sanctions on Tehran in exchange for increased international control over the Iranian nuclear programme and Tehran's commitment not to acquire nuclear weapons.

Its economy suffering under renewed US sanctions, and to put pressure on the European countries still party to the deal, Iran announces on May 8, 2019, that it will no longer uphold two measures it committed to in the pact.

Until this point, Tehran had respected its side of the deal, according to the International Atomic Energy Agency (IAEA).

Iran calls on the European parties to help it circumvent US sanctions.

- Turmoil in the Strait of Hormuz -

From May, while Washington reinforces its military presence in the region, the Gulf sees a series of tension-raising incidents -- six ships are sabotaged or attacked.

Situated between Iran and Oman, the Strait of Hormuz is vulnerable due to its narrowness -- some 50 kilometres (30 miles) -- and its depth of no more than 60 metres (200 feet).

The strait is a vital corridor linking oil producing countries in the Middle East to markets in Asia, Europe and North America.

In 2018 nearly 21 million barrels of crude a day transited the strait, according to the US Energy Information Administration (EIA).

On May 12, the United Arab Emirates says four commercial oil tankers had been targeted by "acts of sabotage" in Gulf waters off its coast.

Washington and Riyadh blame Tehran, which denies involvement.

In the early hours of June 13, two fuel-loaded tankers are hit by mysterious blasts that cause major fires while in Omani waters.

Washington, London and Riyadh accuse Tehran of being behind the attacks, which it denies.

On June 20, Iran's Islamic Revolutionary Guard Corps (IRGC) say they shot down a US drone which violated Iranian airspace.

Washington says the aircraft was in international airspace.

On July 18, Trump says the US military has downed an Iranian drone that came within 1,000 yards of one of its naval vessels in the Strait of Hormuz, "threatening the safety of the ship and the ship's crew".

Iran denies the claim.

- Tankers seized -

Relations between London and Tehran are strained after the seizure on July 4 of an Iranian oil tanker in the British overseas territory of Gibraltar, suspected of attempting to deliver crude to Syria in violation of European sanctions.

Iran denies the ship was destined for Syria and says it will retaliate against this act of "piracy".

On July 10, armed Iranian boats attempt, according to London, to block the passage of a British oil tanker in the Strait of Hormuz.

The Revolutionary Guards deny any "confrontation" with foreign ships.

On July 19, Iran's Guards seize British-flagged tanker Stena Impero in the Strait of Hormuz for "failing to respect international maritime rules".

The seizure comes hours after the Gibraltar Supreme Court said it would extend the detention of the Iranian tanker by 30 days.

Calling the seizure of Stena Impero "utterly unacceptable", London tells British ships to avoid the Strait of Hormuz.

British Foreign Secretary Jeremy Hunt reaffirms "UK desire to de-escalate" tensions with Iran, but adds that the seizure of the Stena Impero was "in clear contravention of international law".

Washington condemns Iran's actions, while Germany, France and the EU call for the tanker's immediate release.

On July 21, Tehran says its investigation into the tanker "depends on the cooperation" of the Stena Impero's crew.

On July 18, Iran had said it detained another foreign tanker and its crew, suspected of "smuggling" fuel into the Gulf.

According to images broadcast by Iranian state TV, the ship, still held by Iran, was flying the Panamanian flag. —AFP