ADEN, Yemen, March 19 (Reuters) - A small bomb exploded in a market in Yemen's southern port city of Aden on Wednesday but caused no casualties, witnesses said, a day after three mortars hit a school near the U.S. embassy in Sanaa.

It was not immediately clear who was behind the bomb, which went off near a bank, but residents said that the market was not busy at the time.

On Tuesday, 13 girls and five Yemeni soldiers were wounded when three mortars hit a school near the U.S. embassy in the Yemeni capital, Sanaa.

Washington said its mission was the target and Yemen said "terrorists" were behind the attack.

Five Yemeni soldiers were also wounded on Tuesday in a bomb attack on a government compound in the southern region of Abyan.

It was not clear if the spate of attacks were related.

Yemen, the ancestral home of Osama bin Laden is viewed in the West as a haven for Islamic militants, dozens of whom are jailed in the Arabian Peninsula country for involvement in bombings of Western targets and clashes with authorities.

Yemen, which joined a U.S.-led campaign against militants after the Sept. 11, 2001 attacks on U.S. cities, has also witnessed a number of militant attacks targeting foreign tourists, oil installations and U.S. and French ships. (Reporting by Mohammed Mokhashef and Mohamed Sudam, Writing by Lin Noueihed, Editing by Sami Aboudi)

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