A tanker sailing off the north coast of Qatar has been attacked, causing an unknown number of casualties, a British maritime security agency said. The attack came as Iran declared it would close a route in the strait of Hormuz being used to circumvent Tehran’s blockade of traffic.

The vessel was in the Gulf, about 500km (300 miles) west of the strait of Hormuz, when it reported being struck “by multiple projectiles”, the UK Maritime Trade Operations said on Wednesday. The UK authority did not specify the origin of the ship.

Wednesday’s attack comes as strikes on tankers sailing through the strait of Hormuz hit their ⁠highest weekly level since the Iran war began, according to maritime security firms, as oil prices to climbed above $100 per barrel.

In the ‌week to 5 October, there were at least 12 attacks ‌on oil, liquefied natural gas and liquefied petroleum gas tankers around the strait, according to data from three security sources.

On Tuesday, India’s ​foreign ministry said 12 crew members were injured after an attack on a Panama-flagged oil tanker passing through the strait of Hormuz.

Attacks, attempted attacks and harassment activity including drone overflights and surveillanceby Iran’s Revolutionary ⁠Guards have persisted in the strait, a US Navy-led agency said on Sunday.

“These actions ⁠continue to demonstrate Iran’s intent to assert presence along key transit lanes ​and maintain pressure on transiting vessels,” ‌the Joint Maritime Information Center said.

Ships in the Gulf and those attempting to transit the strait, the only way in or out of the oil-rich region for vessels, have come under repeated attack since the US and Israel attacked Iran on 28 February.

On Wednesday, Tehran said it would further choke Hormuz, declaring transit routes in the strait deemed illegal by Iran ⁠would soon be closed, in reference to a southern pathway hugging Oman’s coast.

Mohammadreza Naqdi, an adviser to the Revolutionary Guards’ Commander, said these “few routes” had been created by blasting and damaging ⁠some of the rocky passages and were used by “small boats smuggling oil and transferring ⁠it to tankers”, despite evidence Gulf oil exports are regaining ​prewar levels.

“The strait of ‌Hormuz is closed, ‌and the armed forces of the Islamic Republic of Iran have ‌full control over it,” he told the Fars news agency.

The IRGC has consistently denied that seaborne crude flows in the strait are rebounding thanks to US Navy help. IRGC adviser Majid Mirahmadi said on ⁠Thursday that a daily average of 10 ships were transiting the ​waterway against ​an average of 125 before the ​war.

The US secretary of state, Marco Rubio, disputed that account on Wednesday, saying Iran had “lost complete control” of the strait. “There’s almost as much oil flowing out now as there was before this conflict began.”

Amid mixed messaging and supply concerns, the price of oil rose on Wednesday, with Brent crude topping $100 per barrel.

The continuing stalemate in the war is heaping pressure on Donald Trump. The US president is reportedly considering resuming military operations against Iran in the coming weeks, including the option of launching strikes before November’s midterm elections, according to reports in US media.

Last week, a third US aircraft carrier set sail for the region. It could mean that three carriers are in the region as early as the end of October.

As a result of Trump’s war with Iran, Americans have been grappling with high gas prices and soaring diesel costs.

The US has set up its own counter blockade of Iranian ports and occasionally fires on vessels linked to Tehran. It has also bombed Iranian targets in retaliation for Tehran’s attacks on ships, although there have been no such reported strikes since 1 September.

Hormuz is vital to the world economy, with around a fifth of the planet’s oil and liquefied natural gas passing through the strait before the war began.

With Reuters and Agence France-Presse