Dubai. A cargo ship traveling through the Strait of Hormuz on a United Nations-approved route was hit by a projectile on Thursday, the British military said.

The United Kingdom Maritime Trade Operations center reported the attack. It said there were no casualties or any environmental impact.

Several tankers made their way out of the Strait of Hormuz on Thursday using a new route promoted by a UN maritime agency. 

Iran Says New Shipping Route Is ‘Unacceptable’
The naval arm of the Revolutionary Guard, apparently reacting to the new shipping route and increased traffic, issued a warning Thursday, carried by Iran's state-run IRNA news agency.

It said the new route was established without notice or coordination with Iran, calling it “unacceptable and completely dangerous.”

“The only authorized route for passing through the Strait of Hormuz is the one declared by the Islamic Republic of Iran,” the Iranian force said. “Vessel traffic outside these routes is extremely dangerous and prohibited.”

“Violators will be dealt with,” it added, without elaborating.

The opening of an alternative passage through the vital waterway would relieve pressure on the world economy and remove Iran’s main source of leverage in ongoing peace talks with the United States. US Secretary of State Marco Rubio, on a visit to the Gulf to reassure American allies, said Washington was committed to the new route.

Traffic through the strait has increased but is still well below prewar levels. Oil on Thursday briefly dipped below its last prewar price of just under $73 per barrel, a sign that the market believes the situation is improving.

The two sides are still debating the terms of an interim peace deal -- from getting ships through the narrow mouth of the Persian Gulf to the future of Iran’s stockpile of highly enriched uranium.

Under the memorandum of understanding signed last week, the United States and Iran have 60 days to iron out the details. As talks are held behind closed doors, US President Donald Trump and Iranian leaders have seemed to negotiate in public, trading threats and claiming concessions the other side denies.

Oil tankers, led by the Stoic Warrior vessel, sailed along the United Arab Emirates and then Oman early Thursday, passing by Oman's Musandam Peninsula fairly close to the shore. The route was laid out by Oman and the International Maritime Organization, a UN agency.

North of the route is a corridor in the center of the strait where ships had moved through freely before the war, transporting about a fifth of all the world’s oil and natural gas.

Iran said it mined that passage after the US and Israel attacked it on Feb. 28. At least one mine has been sighted there.

Though some ships had been getting out of the strait, with US military support, the UN agency's effort is the latest to free trapped vessels. The shipping company Maersk said its container ship, the Maersk Baltimore, and another chartered vessel made it out on Thursday.

Last week, 125 vessels crossed the strait, up from 33 the week before, according to marine data and analysis firm Lloyd’s List Intelligence.

According to S&P Global, Wednesday saw 78 transits, the most since the war began, but still below the daily prewar average of 130 or more.

“Opportunistic operators -- and there are many of them -- emboldened by the lower transit risk, or at least the perceived lower transit risk, have begun chasing the backlog of trapped cargoes,” said Richard Meade, editor-in-chief at Lloyd’s List.