Global oil prices have jumped after US President Donald Trump said its navy had intercepted and seized an Iran-flagged cargo ship. The Brent crude benchmark oil price rose by more than 4% to $94.20 (£69.60) a barrel, reversing a fall on Friday when Iran said the Strait of Hormuz would be 'completely open' to commercial vessels for the remainder of the ceasefire. On Saturday, Iran announced it would close the strait again, threatening any ship that approached. The waterway is crucial as it typically sees about 20% of the world's oil and liquefied natural gas passing through it. Energy markets have experienced considerable volatility since the US and Israel attacked Iran on 28 February, accompanied by threats from Tehran against shipping in the strait. Trump's announcement has led to speculation and uncertainty in the markets, with analysts noting that investors have grown tired of fluctuating announcements and are focusing more on the actual impact of ongoing geopolitical tensions. Currently, the Strait of Hormuz remains closed, amid ongoing negotiations between US representatives and Iran, which Tehran has stated it has no plans to join for now.