World crude oil futures rose on Friday amid concerns over Iran and Nigeria.

Light, sweet crude for May delivery added 1.55 dollars at 63.38 dollars a barrel on the New York Mercantile Exchange.

Brent crude for June delivery rose 55 cents to 66.49 dollars a barrel on the ICE Futures exchange in London.

The United States said on Thursday that Iran's latest nuclear activities demonstrate its continued defiance of the international community, which will lead possibly to new sanctions. The United States has been demanding Iran, OPEC's No. 2 producer following Saudi Arabia, stop uranium enrichment, which is a necessary step both in nuclear energy making and the making of a nuclear bomb.

Meanwhile, Nigerians will go to polls on Saturday to elect a new president, the first time a civilian government will hand over to another in the country's history. About one-fourth of Nigeria's daily output is still shut after a series of militant attacks. Nigeria is Africa's leading oil producer and the fifth-biggest source of U.S. oil imports.

The Energy Department reported on Wednesday that its crude inventories fell by 1.0 million barrels last week, while its gasoline stockpiles fell 2.7 million barrels.