Iranian drones struck Kuwait’s oil infrastructure on Sunday, causing “severe material damage” that threatened to further disrupt oil supplies already hit by the US and Israel’s war with Tehran.

It came hours before members of the Opec+ group that represents major global oil suppliers gathered to discuss how to bolster output despite Iran’s effective closure of the crucial strait of Hormuz shipping route.

Iran’s Revolutionary Guards said they had attacked petrochemical plants in Kuwait, as well as the United Arab Emirates and Bahrain, with the Kuwait Petroleum Corporation reporting damage and fires at its subsidiaries. The company said fires had earlier broken out at its Shuwaikh oil sector complex, which houses the oil ministry and KPC headquarters, after a separate drone attack.

Iranian drones also reportedly hit an office complex for Kuwaiti government ministries, which caused significant damage but no casualties, while local media reported that two power and water desalination plants had been hit.

It comes as Iran’s central military command rejected an ultimatum by the US president, Donald Trump, who had threatened to destroy the country’s vital infrastructure if Iran did not accept a peace deal within 48 hours. It also followed an Israeli attack on Iran’s petrochemical plants that Iranian media reports said killed at least five people.

The drone attacks on Kuwait are just the latest hit to Middle Eastern oil infrastructure since the US and Israel started the war against Iran at the end of February. Israel’s attack on a production facility in Iran’s largest gasfield at South Pars in mid-March, triggered retaliation by Tehran, which subsequently struck Qatar’s Ras Laffan industrial complex. That came days after drones struck oil storage facilities at the port in Salalah in Oman.

Members of Opec+ – a larger group consisting of members of the Opec oil cartel and other countries – warned on Sunday that repairing energy facilities damaged in recent attacks “is both costly and takes a long time”, and would potentially hit global oil supplies well into the future. They also said the “the critical importance of safeguarding international maritime routes to ensure the uninterrupted flow of energy”.

Meanwhile, Opec+ reportedly agreed in principle to raising oil output by 206,000 barrels a day in May, according to Reuters. However, the agreement remains largely symbolic while Iran continues to effectively block the strait of Hormuz.

The strait is a vital trade artery and typically gives passage to about 100 tankers, carrying 20% of all global crude. Iran’s closure of the narrow waterway has severely constrained the distribution of global oil supplies.

The conflict has now resulted in the largest disruption to oil supplies in history.

The price of Brent crude has soared, rising more than 50% since the start of the year in response to the war and hitting a peak of $119.50 a barrel in March. It is currently trading at about $109 a barrel.

That has pushed up energy costs for consumers, including in the UK and the US, where motorists have been hit hard.

In the UK the average price of a litre of unleaded petrol stood at 154.45p on Sunday, according to the RAC. The average price of diesel is now 185.23p.

Just before the Iran war started, petrol cost 132.83p a litre on average, and diesel was 142.38p a litre.

Last week, average US fuel prices passed $4 a gallon for the first time in four years, and on Sunday the national average was put at $4.110.

Opec+ members had already agreed to increase output by an extra 206,000 barrels a day throughout April in response to the Iran war, at their last meeting on 1 March. The latest meeting suggests members will be poised to again increase output once tankers are allowed safe passage through the strait of Hormuz.