SANAA, April 10 (Reuters) - A blast shook an area near the headquarters of Canadian oil company Nexen <NXY.TO> <NXY.N> in the Yemeni capital Sanaa early on Thursday but there were no casualties, a Yemeni security official said.

A second explosive device was disarmed, the official told Reuters.

The blast followed Sunday's mortar attack that broke windows at a compound housing Americans and other Westerners in Sanaa, which was claimed by an al Qaeda-linked group in the poor Arabian Peninsula country.

The United States on Monday ordered nonessential embassy staff and family members to leave Yemen. It also urged U.S. citizens not to travel to Yemen, viewed in the West as a haven for Islamic militants.

Last month, Al Qaeda claimed responsibility for a mortar attack in Sanaa, which missed the U.S. embassy but wounded girls at a nearby school.

Yemen, the ancestral home of al Qaeda leader Osama bin Laden, has jailed dozens of Islamic militants for involvement in bombings of Western targets and clashes with authorities.

The oil-producing country joined U.S.-led efforts to fight terrorism after the Sept. 11, 2001, attacks on U.S. cities and has itself experienced attacks on foreign tourists, oil installations, and U.S. and French ships.

Yemen is one of the world's poorest countries outside Africa, and a 2007 World Bank report noted domestic crude oil output had declined steadily since 2001. Poverty and unemployment are fuelling discontent in parts of the country.

(Reporting by Mohamed Sudam; writing by Firouz Sedarat)

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