U.S. oil jumps above $75 a barrel after Trump reinstates Strait of Hormuz blockade on Iranian ships

Oil prices jumped Monday after President Donald Trump said the U.S. would reimpose a naval blockade against Iran.

Brent crude futures, the international benchmark, advanced 5.3% to $80 per barrel. U.S. West Texas Intermediate futures were last seen 5.3% higher at $75.18.

"We are reinstating the THE IRANIAN BLOCKADE, so named because it is only stopping Iran's ships or customers from entering or leaving. All other countries will have fair and open use of the Strait," Trump said in a post on his social media platform.

The U.S. military launched another wave of strikes Sunday against Iran after hitting 140 targets on Saturday, according to U.S. Central Command . The strikes are in response to an attack by the Islamic Revolutionary Guard Corps on a container ship transiting Hormuz.

Iran responded Sunday with strikes on U.S. military facilities in Jordan, Kuwait, Bahrain and Oman, according to the state news agency Tasnim .

Iranian state media said the Revolutionary Guard had closed the Hormuz until further notice, but the U.S. military disputed that claim. Centcom said the strait was open to "all vessels seeking to lawfully transit."

"U.S. forces are positioned and prepared to ensure that freedom of navigation remains available despite unwarranted Iranian aggression, harassment, threats, and arbitrary declarations," Centcom said in a social media post Sunday. "Iran does not control the strait. Traffic is flowing."

President Donald Trump said Hormuz was open in an interview with NBC News' "Meet the Press" that aired Sunday. The maritime intelligence firm Windward tracked nine ships that transited the strait on Saturday.

The southern route through Oman's waters remains open to inbound and outbound traffic, said the Joint Maritime Information Center, a U.S.-led naval coalition in Bahrain that provides security updates to civilian ships transiting waters in the Middle East.

But the security situation in Hormuz remains severe, the center said in a notice on Sunday. Mariners should exercise "extreme vigilance," it said.

The weekend airstrikes are the fourth time the U.S. has bombed Iran over the past week in retaliation for attacks on commercial ships transiting Hormuz in the southern corridor protected by the U.S. military.

Iran is demanding ships use a northern route through its territorial waters as it claims control of the strait.

The latest outbreak of fighting stems from conflicting U.S. and Iranian interpretations of how Hormuz was supposed to reopen under an interim peace deal they signed on June 17.

About 20% of the world's oil supplies transited Hormuz before the U.S. and Israel attacked Iran on Feb. 28. Traffic plunged after Iran started attacking ships in the strait in early March, but transits had picked up after Washington and Tehran signed the interim deal.

David Fyfe, chief economist at Argus, said it appears that shipping traffic through the Strait of Hormuz has drastically slowed in the wake of fresh strikes over the weekend.

"Every indication we have is that, over the last couple of days, the actual flow of vessels going through the strait has been really in single digits, compared to 30 or 40 tankers and bulkers going through earlier last week," Fyfe told CNBC's " Europe Early Edition " on Monday.

"So, this has had a real chilling effect on the movement of oil and, you know, we've been drawing down stockpiles consistently since late February when the crisis began. And on top of all of this, we now also have something that has flown under the metaphorical radar, which is Russia cutting off diesel exports to the international market."