Security officials say hundreds of Sudanese troops have arrived in Yemen's southern port city of Aden, the third batch of an expected 10,000 reinforcements for the U.S.-backed Saudi-led coalition fighting the country's Shiite Houthi rebels.

They say Monday's reinforcements come as coalition strikes and clashes rage on in the western province of Taiz, killing three civilians and 20 Houthi fighters. Rebel leaders say they killed 15 pro-government fighters.

Yemen is torn by fighting between the coalition-backed government and the Houthis allied with army units loyal to a former president.

The officials remain neutral in the conflict that has splintered Yemen's armed forces. They spoke on condition of anonymity because they are not authorized to speak to reporters, as did the rebel leaders.