The US Fifth Fleet said on Thursday that its vessels have received distress calls from two tankers reportedly under attack in the Gulf of Oman. "We are aware of the reported attack on tankers in the Gulf of Oman," said a statement from the Fifth Fleet, based in Bahrain. "US naval forces in the region received two separate distress calls at 6:12 am. local time and a second one at 7:00 am," the statement said. "US Navy ships are in the area and are rendering assistance." Two tankers, the Marshal Islands-flagged Front Altair and the Panama-flagged Kokuka Courageous, had been evacuated and the crews were safe, four shipping and trade sources said. The United Kingdom Maritime Trade Operations, part of the Royal Navy, earlier said it was aware of an incident in the Gulf of Oman. "UK and its partners are currently investigating," the group said without elaborating. Oil prices surged by 4 percent after the report that raises tensions in the Gulf, which have been heightened by a dispute between Iran and the United States. A spokesman for the Kokuka Courageous tankers manager BSM Ship Management (Singapore) said 21 crew had abandoned ship after the incident, which resulted in damage to the vessel’s starboard hull. The master and crew were quickly rescued from a lifeboat by the Coastal Ace, a nearby vessel. One crew man from the Kokuka Courageous was slightly injured in the incident and received first aid on board the Coastal Ace. "The Kokuka Courageous remains in the area and is not in any danger of sinking. The cargo of methanol is intact," the spokesman said. As for Front Altair, which was chartered by Taiwans state oil refiner CPC Corp to carry fuel, a senior company official said that the vessel was carrying 75,000 tons of naphtha, a petrochemical feedstock, when it was "suspected of being hit by a torpedo. Wu I-Fang, CPCs petrochemical business division CEO, told Reuters that all crew members have been rescued. Frontline confirmed its tanker Front Altair was on fire after the Gulf of Oman incident, Norwegian Newspaper VG reported. A Frontline spokesman said however that all crew members were brought to safety, according to the daily. The UAE had said that May 12 attacks on four vessels off the coast of Fujairah were likely caused by limpet mines and bore the hallmarks of an operation most likely by a state actor. Saudi Arabias envoy to the United Nations blamed Iran.