By Lisa Barrington and Rania El Gamal

DUBAI (Reuters) – Attacks on two oil tankers on Thursday in the Gulf of Oman left one ablaze and both adrift, shipping firms said, driving oil prices up 4% over worries about Middle East supplies.

The Front Altair was on fire in waters between Gulf Arab states and Iran after an explosion that a source blamed on a magnetic mine. The crew of the Norwegian vessel were picked up by a vessel in the area and passed to an Iranian rescue boat.

A second Japanese-owned tanker was abandoned after being hit by a suspected torpedo, the firm that chartered the ship said. The crew were also picked up.

The attacks were the second in a month near the Strait of Hormuz, a major strategic waterway for world oil supplies.

The United States and Saudi Arabia blamed Iran for last month’s attacks using limpet mines on four tankers off the coast of the United Arab Emirates, a charge Tehran denies.

There were no immediate statements apportioning blame after Thursday’s incidents.

“We need to remember that some 30% of the world’s (seaborne) crude oil passes through the straits. If the waters are becoming unsafe, the supply to the entire Western world could be at risk,” said Paolo Amico, chairman of INTERTANKO tanker association.

Tensions have risen since President Donald Trump, who has demanded Tehran curb its military programs and influence in the Middle East, pulled the United States out of a deal between Iran and global powers to curb Tehran’s nuclear ambitions.

Thursday’s attacks came as Shinzo Abe – prime minister of U.S. ally Japan, a big importer of Iranian oil until Washington ratcheted up sanctions – was visiting Tehran with a message from Trump. Abe urged all sides not to let tensions escalate.

The Bahrain-based U.S. Navy Fifth Fleet said it was assisting the two tankers on Thursday after receiving distress calls. Britain said it was “deeply concerned” about Thursday’s reported explosions and was working with partners on the issue.

Iranian Foreign Minister Mohammad Javad Zarif described Thursday’s incidents as “suspicious” on Twitter, noting they occurred during Abe’s Tehran visit. The minister called for regional dialogue.

Oman and the United Arab Emirates, which both have coastlines along the Gulf of Oman, did not immediately issue any public comment.

Saudi Arabia and the UAE, both majority Sunni Muslim nations with a long-running rivalry with predominantly Shi’ite Iran, have previously said attacks on oil assets in the Gulf pose a risk to global oil supplies and regional security.

EXPLOSION

Bernhard Schulte Ship management said the Kokuka Courageous was damaged in a “suspected attack” that breached the hull above the waterline while transporting methanol from Saudi Arabia to Singapore.

It said the ship was afloat and the crew safe with one minor injury reported.

A shipping broker said the blast that struck the Kokuka Courageous might have been caused by a magnetic mine. “Kokuka Courageous is adrift without any crew on board,” the source said.

Japan’s Kokuka Sangyo, owner of the Kokuka Courageous, said its ship was hit twice over a three-hour period.

Taiwan’s state oil refiner CPC said the Front Altair, owned by Norway’s Frontline, was “suspected of being hit by a torpedo” around 0400 GMT carrying a Taiwan-bound cargo of 75,000 tonnes of petrochemical feedstock naphtha, which Refinitiv Eikon data showed had been picked up from Ruwais in the UAE.

Frontline said its vessel was on fire but afloat, denying a report by the Iranian news agency IRNA that the vessel had sunk.

Front Altair’s 23-member crew abandoned ship after the blast and were picked up by the nearby Hyundai Dubai vessel. The crew was then passed to an Iranian rescue boat, Hyundai Merchant Marine said in a statement.

Iranian search and rescue teams picked up 44 sailors from the two damaged tankers and took them to the Iranian port of Jask, Iran’s IRNA reported.

Thursday’s attacks came a day after Yemen’s Iran-aligned Houthis fired a missile on an airport in Saudi Arabia, injuring 26 people. The Houthis also claimed an armed drone strike last month on Saudi oil pumping stations.

Iranian Supreme Leader Khamenei told Abe during his visit to Iran that Tehran would not repeat its “bitter experience” of negotiating with the United States, state media reported.

“I do not see Trump as worthy of any message exchange, and I do not have any reply for him, now or in future,” the Iranian leader said.

(Reporting by Koustav Samanta and Jessica Jaganathan in Singapore, Liang-Sa Loh and Yimou Lee in Taipei, Terje Solsvik in Oslo, Ghaida Ghantous in Dubai, Hyunjoo Jin in Seoul and Jonathan Saul in London; Writing by Edmund Blair; Editing by Jon Boyle and Alison Williams)