"It's a headache for North Asian refiners who are heavily reliant on Middle East oil supplies. We are currently monitoring the situation. It's an unfavourable factor for the overall crude oil market ... driving up prices," said a North Asian oil refining source, declining to be named due to company policy.
Asia gets nearly 70 percent of its crude oil from the Middle East, and any disruption to oil production, loading facilities or key shipping routes such as the Strait of Hormuz could have a severe impact on Asian economies. Oil tankers typically refuel at UAE's Fujairah port, one of the world's largest bunkering hubs, where the ship attacks occurred.
Following Sunday's attack on oil tankers, oil and shipping companies said they would have to alter their routes or take precautions near Fujairah.
"We had a ship which was refuelling at Fujairah when the incident occurred. Fortunately nothing happened," said KY Lin, spokesman at Taiwan's Formosa Petrochemical Corp.
"There are no other (bunkering) choices nearby. We may choose to refuel at Singapore instead," Lin said.
Japanese shipper Nippon Yusen has already decided to refrain from sending tankers to Fujairah for bunkering, maintenance or crew swaps except for emergencies, a company spokesman said.
If its tankers need to anchor at the port, they are advised to shorten their stay as much as possible, the spokesman said.
Ashok Sharma, managing director of shipbroker BRS Baxi in Singapore said: "There seems to be no increase in risk (insurance) premia as of yet."
Risk premium increases would be inevitable, however, if security in the region continued to deteriorate, he added.
NO LOADING DISRUPTIONS SO FAR
Noriaki Sakai, an executive officer at Idemitsu Kosan Co Ltd, Japan's second-largest refiner, told reporters on Wednesday that while there is no impact on oil loading or ship operations, the company is closely watching the situation.
The second set of attacks was on Saudi Arabia's Petroline, which mainly transports light crude from the kingdom's eastern fields to its western port of Yanbu.
Saudi oil exports to Asia were not disrupted because ships chartered by Asian refiners call mainly at the ports of Ras Tanura and Juaymah in the Gulf, the industry sources said.
But Petroline is important because it is an alternative route for Saudi Arabia's oil exports that bypasses the Strait of Hormuz, one of the sources said.
"This attack doesn't affect physical supply, but the psychological effect is big," the source said.
The pipeline attacks "likely represent an Iranian effort to expose the vulnerabilities of oil export infrastructure that can bypass the Strait of Hormuz," analysts with risk advisor and consultancy Eurasia Group said in a note.
U.S. security agencies believe proxies sympathetic to or working for Iran may have attacked the four tankers at Fujairah rather than Iranian forces themselves, a U.S. official familiar with the latest U.S. assessments said on Tuesday.
Iran has denied any involvement in the attacks.
(Reporting by Yuka Obayashi in TOKYO and Florence Tan in SINGAPORE; Additional reporting by Jane Chung in SEOUL, and Chen Aizhu and Roslan Khasawneh in SINGAPORE; Editing by Tom Hogue) ((Florence.Tan@thomsonreuters.com; +65 6870 3497; Reuters Messaging: email@example.com))