Crude oil prices edged up on Thursday as demand was estimated to have remained strong despite slowing growth in Asian economies, and as Russian and western air campaigns in Syria worried markets. World oil demand surged in the first six months this year against the same period in 2014, due to a halving in crude oil prices and significant declines in the price of most fuels in many consuming countries, according to national estimates submitted to the Joint Oil Data Initiative (JODI). JODI reported consumption averaged 71.4 million barrels per day (bpd) in the first six months of 2015, up from 69.1 million bpd in the year-ago period, an increase of 2.3 million bpd or 3.3 percent. Traders also said that a political risk premium had re-entered oil markets over Syria, where Russia and the United States are both carrying on bombing campaigns without coordination, triggering fears of unintentional clashes. In U.S. markets, hurricane Joaquin strengthened in the Atlantic and could become a major storm, the U.S. National Hurricane Center said, although forecast models did not agree on whether it would make landfall in the United States. U.S. West Texas Intermediate (WTI) futures CLc1 were at $45.71 a barrel at 0456 GMT, up 62 cents from their last settlement. Brent crude futures LCOc1 were at $48.75 per barrel, up 38 cents. CHEAPER PHYSICAL CRUDE Despite stronger crude futures, physical crude markets weakened amid concerns over whether the growth in consumption could last if slowdowns continue in Asia's leading economies. Asia's benchmark physical price, Dubai crude, averaged $45.375 a barrel for September, the lowest since February 2009, traders said on Thursday. South Korea's crude oil imports in September fell 0.8 percent from a year earlier to 76.1 million barrels, preliminary official data showed. Across Asia, there were more signs of economic slowdown. In China, Asia's biggest economy, activity in the manufacturing sector contracted for a second straight month in September, an official survey showed on Thursday. In Asia's second-largest economy, Japan, manufacturers' confidence worsened in the three months to September, a central bank survey showed, as they felt the pinch from volatile financial markets and slumping shipments to China. Data from Indonesia and Malaysia implied a worsening economic outlook for Southeast Asia, and Morgan Stanley said it expected "growth in ASEAN4 (Singapore, Philippines, Indonesia and Thailand) will likely be lower for longer." Asia's slowdown contributed to a fall in Brent and WTI prices by almost a quarter since June.