At 2:45pm (0645 GMT), New York's main contract light, light sweet crude for May delivery, was up 52 cents at 69.84 dollars a barrel from its close of 69.32 dollars in US trading Thursday. US markets were closed on Good Friday.

On Monday, the contract hit a high of 70 dollars flat before easing slightly.

Two key issues were driving the market, said Victor Shum, an analyst with energy consultancy Purvin and Gertz in Singapore.

"One is the gasoline supply situation in the US and two is the issue over Iran," he said. "The issue is still there and it will continue to be with us."

Concerns of a possible US-Iran military conflict heightened after Tehran warned Washington Sunday against attacking its nuclear facilities, saying it had tens of thousands of would be suicide bombers at the ready and could count on the support of militants across the region.