Oil-producing countries have pledged to pump more crude into the market as they aim to take advantage of a looming price surge triggered by the crisis in Iran.

The Organisation of Petroleum Exporting Countries (Opec) said on Sunday it would jack up output by 206,000 barrels a day, almost two-thirds more than the expected increase.

The cartel said the move would “provide an opportunity for the participating countries to accelerate their compensation”.

Opec, a producer cartel that includes Saudi Arabia, Iraq, Kuwait and the United Arab Emirates (UAE), took action amid fears that oil prices could race towards $100 a barrel when markets reopen on Sunday night, up from $73 on Friday.

Brent crude jumped 10pc to about $80 a barrel on Sunday in over-the-counter trades, which take place outside exchanges, after US and Israeli strikes on Iran led to disruption of fuel shipments in the region.

Reports suggest the Iranian navy is telling at least some vessels that Tehran has banned traffic in the Strait of Hormuz, a crucial shipping lane where roughly a fifth of oil destined for the world market passes through.

Tankers are still moving through the Strait but in much smaller numbers, with 150 vessels anchored just outside its mouth. Two vessels have already been hit off the coast of Oman, although the circumstances remain unclear.

There has been no formal announcement from Iran, creating uncertainty and confusion.

Risks were heightened after the Yemen-based Houthi militia, which is backed by Tehran, said it would restart attacks on shipping in the Red Sea corridor.

Amid fears of higher petrol prices in Britain, Howard Cox of campaign group FairFuelUK urged Rachel Reeves to freeze fuel duty for the remainder of parliament in Tuesday’s Spring Statement.

John Healey, the Defence Secretary, said the Chancellor was “watching very closely, as you’d expect, any movement in the oil price” but downplayed the prospect of immediate action. He told Sky News: “We’re less than 48 hours into this current conflict.”

Investors are braced for volatility in oil prices and broader financial markets on Monday.

“There will be a significant reaction when markets open. We could see huge disruption to energy markets, as the conflict may widen and escalate further,” said Neil Wilson, a Saxo Bank strategist.

As well as oil, gold prices are expected to jump while futures suggest the FTSE 100 and markets on Wall Street will fall by around half a percent.

While Opec’s promise of more supply should theoretically temper surging oil prices, tankers from countries such as Saudi Arabia and the UAE must sail through the Strait – meaning the certainty of supply is in doubt.

Commercial shipping companies have already started suspending ship movements not only through Hormuz but also across the Middle East.

Global shipping giant Hapag-Lloyd said its suspension of shipping through Hormuz, announced over the weekend, would continue “until further notice” and warned of “delays, rerouting and schedule adjustments”.

France’s CMA CGM has suspended passage through the Suez Canal, and Japanese giant Nippon Yusen has reportedly told its fleet to avoid Hormuz. Maersk is redirecting container traffic from the Middle East to the longer route around Africa.

Analysts said the Strait of Hormuz’s potential closure could push prices towards $100 a barrel.

“It’s an extremely fluid situation but as things stand right now, we believe we will probably test that level on Monday. How long the spike lasts would depend on how the situation unfolds,” Amarpreet Singh, a Barclays analyst, said in a note.

Opec had been holding output back, with many oil-exporting countries worried that a potential supply glut would push prices down to uneconomic levels for their producers.

But the price has instead climbed almost 20pc this year, as Donald Trump moved warships to the region and buyers and traders began pricing in the risk of a US-Israeli strike on Iran.

Saudi Arabia has spare production capacity of 1.8 million barrels a day, and the UAE may also be able to loosen the spigot by up to one million barrels a day. Most other producers might struggle.

Richard Bronze, of market analysis firm Energy Aspects, said: “We think the group can only manage about half the announced increase given many countries lack spare capacity. Saudi Arabia will account for most of this volume.”

Mr Singh said the US could potentially ease the price squeeze by releasing stocks from its strategic petroleum reserve. However, a US energy official told the Financial Times at the weekend there had been “no discussions at all” about tapping the reserve.

An oil price of $100 a barrel, if sustained, would prompt faster inflation and prevent central banks from any further interest-rate cuts. It would drive up costs for businesses, potentially putting a brake on economic growth.

The crisis has already fuelled chaos in the global aviation industry, which would suffer further as a result of higher oil prices.

Airspace over the Middle East remained closed and flight cancellations continued to disrupt some of the world’s busiest air transport hubs.

Emirates, Etihad and Qatar Airways are yet to resume flights, leaving tens of thousands of passengers stranded at three of the world’s busiest airports: Dubai, Abu Dhabi and Doha.

Many other airlines are caught up in the chaos, which has left passengers and crew stranded across the network.

None of the airlines gave any indication as to when flights would resume, saying they would issue fresh updates early on Monday UK time.

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