Brent crude oil shot up nearly 6 percent today after Saudi Arabia and its Gulf Arab allies began a military operation in Yemen, although importers saw little immediate threat to supplies.
The strike against Houthi rebels, who have driven the president from Yemen's capital Sanaa, could stoke concerns about the security of Middle East oil shipments.
Oil prices jumped as traders and importers said they were worried the Saudi attack was a sign that fighting in the oil-rich Middle East was out of control and spreading.
Brent futures rose as high as $59.71 (40 pounds) a barrel, up almost 6 percent since their last settlement, before dipping back to $59.10 a barrel, though still up over $2.60.
U.S. crude was up $2.55 at $51.76 a barrel.
The risk from the attack in Yemen was heightened because the Houthis have received some support from Iran, Saudi Arabia's long-time rival for dominance in the Middle East.
China's foreign ministry said on Thursday it was deeply concerned about the worsening situation in Yemen.
Ministry spokeswoman Hua Chunying told a news conference that China urged all parties to act in accordance with United Nations Security Council resolutions on Yemen, and to resolve the dispute through dialogue.
"The Saudis have taken military action because they have said the Houthis are getting support from the Iranians," said Li Guofu, director of the Centre for Middle East Studies at the China Institute of International Studies.
"This is an indication that the war may gradually spread into a regional conflict. This is something the Chinese government is very much concerned about."
SURGING OUTPUT
Beyond oil, the Middle East is also the world's biggest exporter of liquefied natural gas (LNG), from Qatar and also Yemen, but importers said they were not immediately worried.
"Gas supply from Yemen has no disruption so far. We are not concerned given the supply surplus and weak demand currently," said Lee Sang-wook at Korea Gas Corp.
Like oil, LNG prices have fallen by more than half in the last 10 months as surging output has been met with slowing economic growth, especially in Asia.
With the global crude glut built up from U.S. shale oil and strong output from producers such as Russia, there is little immediate worry about any shortages developing.
"Just because Saudi and others conducted air strikes doesn't mean the oil market becomes suddenly tight," said Masaki Suematsu, manager of the energy team at brokerage Newedge Japan in Tokyo, although he cautioned that the conflict could spiral further beyond the airstrikes.
Some analysts said the strikes could lead to more stability in the region, if it resolved the conflict in Yemen.
"If this is a prelude to a bigger operation in the Middle East, that may lead to some stability in the region," said Mari Iwashita, chief market economist at Tokyo's SMBC Friend Securities.
Asian officials also said the fighting occurred near the Red Sea, waters that Arab Gulf supplies do not pass on their way to Asia. European importers may be more concerned as Arab producers have to ship oil past Yemen's coastlines via the Gulf of Aden to get to the Suez Canal.
The waters between Yemen and Djibouti, at less than 40 km (25 miles) wide, are considered a "chokepoint" to global oil supplies by the U.S. Energy Information Administration and the region is heavily militarized by western navies.