Rival Yemen army units in brief clash near Hadi

The exchange was between troops from the First Armoured Division, commanded by a general who mutinied last year against former President Ali Abdullah Saleh, and the central security force led by Saleh's nephew. There were no reported casualties.

The clash comes less than a week after Hadi was sworn in under a U.S.-backed Gulf Arab plan aimed at averting civil war in the impoverished Arabian peninsula state, where Islamists linked to its wing of al Qaeda have seized chunks of territory during a year of political turmoil over Saleh's fate.

Mass protests against Saleh were followed by fighting between forces loyal to him, those of rebel general Ali Mohsen and militiamen backed by tribal leaders, leaving parts of the capital in ruins and raising fears of civil war in a country on key oil shipping routes.

Saudi Arabia and Washington, the target of abortive attacks by the country's wing of al Qaeda, backed Hadi in a single-candidate election aimed at starting a two-year transition during which the military is to be restructured.

Al Qaeda claimed responsibility for a suicide attack that killed as many as 26 people in the southern city of Mukalla hours after Hadi was sworn in, calling the strike revenge for the crimes of Yemen's Republican Guard, led by Saleh's son.

Hadi has vowed to pursue the campaign against al Qaeda in Yemen, where Washington has used drone strikes - including one to assassinate a U.S. citizen it accuses of plotting a failed attack - against alleged members of the group.

(Reporting by Mohammed Ghobari; Writing by Joseph Logan; Editing by Alison Williams)