Two oil tankers, including one operated by a Tokyo-based company, were attacked Thursday near the strategically important Strait of Hormuz, pushing up oil prices and fueling concerns about further tensions in the Middle East.

In Washington, Secretary of State Mike Pompeo blamed Tehran for the attacks, citing U.S. assessment based on intelligence, type of weapons used and level of expertise needed to carry out the operation.

(Attacked Japanese tanker pictured on June 13, 2019, at Japanese company Kokuka Sangyo.)

Pompeo said Iran "insulted Japan" by attacking the Japanese-owned vessel, the Kokuka Courageous, at the time of Prime Minister Shinzo Abe's landmark visit to Iran for talks with the country's leaders aimed at defusing tensions between Tehran and Washington.

The Kokuka Courageous was left ablaze and drifting in the attacks. The other vessel caught fire, as well.

All 44 crew members in the two tankers were safe, though one of them was slightly injured.

Japan's transport ministry said details of the attacks and the extent of damage are not yet known, and the Japanese tanker is currently drifting without any crew aboard.

Yutaka Katada, president of Kokuka Sangyo Co., operator of the Kokuka Courageous, expressed anger at the incident.

"I don't know why our ship was attacked," Katada told reporters in Tokyo. "I'm angry that the lives and safety (of the crew) were threatened."

Speaking in Washington, Pompeo said, "This is only the latest in a series of attacks instigated by the Islamic Republic of Iran and its surrogates against American and allied interests."

The chief U.S. diplomat was referring to a similar attack on four commercial ships in the area and the bombing of an oil pipeline in Saudi Arabia by Iranian-backed fighters, both in May.

"Taken as a whole, these unprovoked attacks present a clear threat to international peace and security, a blatant assault on the freedom of navigation, and an unacceptable campaign of escalating tension by Iran," he said.

In New York, U.N. Secretary General Antonio Guteress strongly condemned the attacks, warning that the world cannot afford "a major confrontation in the Gulf region."

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The attacks near the Strait of Hormuz, a key corridor through which a third of all oil traded by sea passes, caused global oil prices to surge.

West Texas Intermediate jumped 3.5 percent to 53 dollars a barrel at one point, while Brent crude soared 4.5 percent to 62 dollars a barrel.

Despite the surge, Japanese industry minister Hiroshige Seko told reporters there was no immediate threat to the country's energy supply.

The Kokuka Courageous was carrying 25,000 tons of methanol from Saudi Arabia to Singapore when it was attacked with what appeared to be artillery shells in the Gulf of Oman, near the Fujairah port of the United Arab Emirates, according to Kokuka Sangyo.

All 21 Filipino crew members of the Panama-flagged ship escaped in life rafts and were rescued by a ship heading to the United Arab Emirates, according to Kokuka Sangyo. A Singapore-based firm that manages the ship said one crew member was slightly injured.

The U.S. Navy's 5th Fleet said it received distress signals from the Kokuka Courageous and another tanker at 6:12 a.m. and 7:00 a.m.

A hole that appeared to have been caused by some kind of artillery shell was found on the ship, the company said, adding that a fire broke out in the ship's engine room but was extinguished by the crew before they abandoned ship.

(U.S. Navy says footage shows an Islamic Revolutionary Guard Corps patrol boat approaching Kokuka Courageous and removing a limpet mine.) 
[Video courtesy of U.S. Navy]

The other ship, the Marshall Islands-listed Front Altair, was chartered by Taiwanese oil refiner CPC Corp. to carry 75,000 tons of naphtha from the UAE to southern Taiwan, company Vice President Chen Ming-hui said.

Chen said the vessel was "engulfed in flames" but all 23 crew members were safe.