Crude prices surged Monday on unrest in Nigeria ahead of the U.S. summer gasoline season.

Light, sweet crude gained 1.33 dollars to 66.27 dollars a barrel on New York Mercantile Exchange.

London Brent was up 1.07 dollars to 70.49 dollars after trading as high as 70.83 dollars earlier.

Unknown assailants broke into an unused Nigerian oil well operated by Total on Monday, causing a minor spill, said the company.

However, rising violence in Nigeria has cut a third of the OPEC nation's oil output and forced thousands of expatriates to evacuate.

Prices also drew support as Iran, the world's No. 4 oil exporter, pressed ahead with its atomic work.