Iran fired on three ships in the Strait of Hormuz and seized two of them on Wednesday, intensifying its assault on shipping in the key waterway. The attacks came a day after U.S. President Donald Trump extended a ceasefire while maintaining an American blockade of Iranian ports.

The standoff between the U.S. and Iran has effectively choked off nearly all exports through the strait — where 20% of the world’s traded oil passes in peacetime — with no end in sight. Iranian media said the paramilitary Revolutionary Guard was bringing the two ships to Iran, marking a further escalation, though the White House said the seizures didn’t violate ceasefire terms.

The conflict has already sent gas prices skyrocketing far beyond the region and raised the cost of food and a wide array of other products. The price of Brent crude oil, the international standard, nosed over $100 per barrel, marking a 35% increase from prewar levels, but stock markets still appear to be shrugging it off.

The European Union energy commissioner, Dan Jorgensen, warned of lasting impact for consumers and businesses, likening it to other major energy crises over the last half-century. He said the disruption is costing Europe about $600 million each day.

Iran holds firm in apparent tit-for-tat

Iranian media said the MSC Francesca and the Epaminondas were being escorted to Iran. The U.S. had earlier seized two Iranian vessels as the ceasefire talks were due to take place in Pakistan.

Technomar, the management company behind the Liberian-registered Epaminondas, said it was “approached and fired upon by a manned gunboat” off the coast of Oman. It said the ship’s bridge was damaged.

A second cargo ship came under fire hours later, with no report of damage, though it was then stopped in the water. No injuries to the crews of either vessel were reported. Panama condemned what it called the “illegal seizure” of the Panama-flagged MSC Francesca, and said it represented a serious attack on maritime security.

The Guard attacked a third ship, identified as the Euphoria, which had become “stranded” on the Iranian coast, Iranian media reported, without elaborating.

Still, Iran’s seizure of the ships didn’t violate truce terms because “these were not U.S. or Israeli ships, these were two international vessels,” White House press secretary Karoline Leavitt told Fox News Channel.

There have been more than 30 attacks on ships in the Mideast since the U.S. and Israel launched the war on Feb. 28 with a surprise attack on Iran. Before then, the strait was open for all traffic.

Vortexa, an analytics firm focusing on global energy and freight markets, said it has recorded 34 movements of sanctioned and Iranian-linked tankers in and out of the Persian Gulf in the week after the U.S. imposed its blockade on April 13.

The firm identified 19 outbound and 15 inbound movements. Six of the outbound movements were “confirmed laden with Iranian crude, representing about 10.7 million barrels,” it said in an email. It was not immediately clear whether all those barrels reached markets overseas.

It’s not clear when talks will restart

Iran’s ability to restrict traffic through the strait — which leads from the Persian Gulf to the open ocean — has proved a major strategic advantage

While the ceasefire means American and Israeli airstrikes have stopped in Iran — and Tehran’s missiles no longer target Israel and the wider Middle East — the maritime standoff continues and could escalate.

Without any diplomatic agreement, the attacks will likely deter ships from even attempting to pass through the waterway, further squeezing global energy supplies.