Al-Qaida-linked militants in Yemen are demanding a $12 million ransom for the release of three French aid workers who went missing in May.

Yemeni security officials and tribesmen revealed the demand on Wednesday.

The two women and one man disappeared in the eastern city of Sayoun, where they had been working with a French-based relief agency.

French and Yemen authorities previously said the aid workers were probably kidnapped but had no definite word on their status.

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

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 Yemeni President Ali Abdullah Saleh.

He also said he supports the anti-government protests in Yemen that seek to oust Mr. Saleh after 33 years in power.

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 Yemen's anti-government unrest to expand their haven in the country and plot attacks against the West.