Yemen tribal leader held under house arrest over al Qaeda ties ADEN (Reuters) - A tribal leader suspected of links to al Qaeda was put under house arrest on Saturday in the southern city of Aden after security forces warned him a week ago to hand himself over to the authorities, an official said. Yemen has stepped up a campaign to defeat Islamist militants this year. It is an arena for U.S. drone strikes because al Qaeda in the Arabian Peninsula has used its Yemen base to target Saudi Arabia and the United States. Tarek al-Fadli, who was raised in Saudi Arabia and fought in Afghanistan, heads a major tribe in Abyan province. He disappeared several months ago when the Yemeni army, backed by U.S. drones, fought to clear al Qaeda militants from southern Yemeni towns they had occupied during an uprising last year against veteran ruler Ali Abdullah Saleh. Fadli reappeared last week in his home in the port city of Zinjibar, one of the towns the army took back from al Qaeda, leading to a stand-off between his supporters and troops. On Tuesday, he was given an ultimatum to surrender as the government sought to avoid a clash with the tribal leader. Fadli agreed on Saturday to move to the southern capital of Aden where he was placed under house arrest. "We managed to move Fadli out of his home in Abyan and now he's under house arrest in Aden," said an official from Abyan. Now Fadli will remain under house arrest until the people of Abyan present evidence that would lead to his trial. The stand-off, which lasted nearly a week, highlighted the challenges facing President Abd-Rabbu Mansour Hadi - who took power after Saleh stepped down in February - in trying to assert state authority following the uprising. Its wealthier Gulf neighbors and Washington are concerned al Qaeda and other Islamist fighters could pose a threat to Saudi Arabia and nearby oil shipping channels. Reporting by Mohammed Mukhashaf; Writing by Amena Bakr; Editing by Sophie Hares