The head of al-Qaida's offshoot in Yemen has vowed loyalty to Osama bin Laden's successor and promised to keep fighting against the Western-allied government in Sana'a.

In a 10-minute audio message posted on Islamist websites Tuesday, Nasser al-Wahishi said his organization officially recognizes Ayman al-Zawahiri as al-Qaida's new global leader.

The terror group proclaimed the 60-year-old Egyptian its chieftain following bin Laden's death in a U.S. military raid on his Pakistani compound in May.

Wahishi said al-Qaida in the Arabian Peninsula will fight until it overthrows the government of embattled Yemeni President Ali Abdullah Saleh. He said he supports the anti-government protests in Yemen that seek to oust Mr. Saleh after 33 years in power.

Wahishi also criticized the rulers of neighboring Saudi Arabia. Saudi and Yemeni leaders both consider the al-Qaida chieftain among their most wanted terrorists.

The United States says the Yemeni branch is al-Qaida's most active. The group has been linked to several attempted attacks on U.S. targets.

Washington fears al-Qaida-linked militants will take advantage of the unrest in Yemen to expand their haven in the country and plot attacks against the West.

On Monday, armed tribesmen in southern Yemen said they had routed Islamist militants from most of Zinjibar, the capital of volatile Abyan province.

Tribal sources said fierce clashes sent many militants from the group Ansar Shariah, or supporters of Islamic law, fleeing north to the town of Lawdar, where again they were repelled.

An estimated 90,000 civilians have fled Abyan to escape the violence as the army and tribesmen confront the Islamists.