Two explosions followed by heavy gunfire went off outside the U.S. embassy in Yemen on Wednesday, and smoke was seen rising from the heavily-fortified compound, witnesses said.

Al Arabiya Television said that the initial blast was caused by a suspected car bomb and that there were believed to be casualties.

Yemeni officials were not immediately available to comment on the cause of the blasts or the number of casualties, but ambulances and fire engines rushed to the scene and police cordoned off the area.

A U.S. embassy official declined to comment.

Yemen, the ancestral home of Osama bin Laden, has grappled with a spate of al Qaeda attacks this year, including one on the U.S. embassy, another near the Italian mission and others on Western tourists.

An al Qaeda-affiliated group claimed responsibility in March for a mortar attack that missed the U.S. embassy in Sanaa but wounded 13 girls at a nearby school.

The United States ordered non-essential staff to leave Yemen in April, a day after an attack on a residential compound.

The Yemeni government joined the U.S.-led war against terrorism following the Sept 11, 2001 attacks on U.S. cities.

The government of the poor Arab country has also been fighting Shi'ite rebels in the northern province of Saada since 2004 and faced protests against unemployment and inflation.