Crude oil futures gained 3% on 6 April after Saudi Arabia raised prices for crude sales to Asia for a second month, indicating better demand in the region.

Brent May contract was trading 3.29% higher to $56.76 a barrel at 08.21am GMT.

US May contract was trading 3.42% higher to $50.82 a barrel.

Saudi's flagship Arab Light crude competes with oil from Oman and the UAE.

Shunling Yap, a senior oil and gas analyst at BMI Research, told Reuters: "There is still competition for the Asia market even though it is also a sign that some of the production elsewhere is less able to compete in the market right now."

Last week, the Brent May contract lost some 2.7%, on speculation that a preliminary nuclear deal between Iran and Western powers could ease sanctions on the Opec member, potentially flooding the markets with Iranian oil.

But analysts warned that ramping up exports could take months and was unlikely to happen before 2016.

Morgan Stanley said in a note: "While clearly a bearish headline, a final deal and full lifting of sanctions still faces a number of obstacles.

"Even if a final deal is reached, we do not expect any physical market impact before 2016."

Saudi Arabia, the world's top oil exporter, left output unchanged and lowered its official selling prices (OSPs) sharply late last year, in a battle for market share amid a global supply glut.