An attack on a commercial vessel in the Strait of Hormuz on Saturday triggered another round of U.S. strikes on targets in Iran and threatened to unsettle energy and financial markets further, after a tumultuous week of hostilities around the Persian Gulf.

Daily ship traffic through the strait, which normally carries a fifth of the world’s oil, recently dropped to the lowest level in weeks, with the latest data showing only 22 ships braving the passage on Thursday, according to Kpler, a maritime data firm. More than 130 vessels passed through daily before the war.

Brent crude oil, the international benchmark, closed the week near $76 per barrel, about 5 percent higher than prewar levels. Although far below the peak of nearly $120 a barrel during the worst of the war, the market moves that follow each round of strikes have shown Iran’s capacity to move energy prices.

If recent patterns are repeated, trading could be volatile when markets reopen on Sunday night.

Iran insists that its waters are the only viable route through the Strait of Hormuz for commercial vessels. Ships instead taking a route close to Oman’s coastline, guided and protected by the U.S. military, have drawn Tehran’s wrath. The vessel attacked this weekend was in Omani waters, as were the ships hit earlier in the week, sparking the latest cycle of tit-for-tat retaliation.

“Iran would like there to be nothing flowing through the Omani lane, and they have not been able to stop all of what’s happening,” Daniel Sternoff, a senior fellow at Columbia University’s Center on Global Energy Policy, told The New York Times this week.

The middle of the strait, where ships traveled before the war, is considered dangerous because of the risk of mines laid by Iran’s military.

Iran’s attacks on ships have come after years of observing how the Houthi militia in Yemen, proxies of Iran, managed to threaten shipping in the Red Sea. Red Sea traffic is at only 55 to 60 percent of what it was before 2023, when the Houthis began attacking ships in that waterway in retaliation for Israel’s war in Gaza.

Peter Eavis, Jenny Gross and Eric Schmitt contributed reporting.