Gunmen, believed to be militants linked to al Qaeda, attacked a minibus carrying intelligence officers in southern Yemen on Wednesday, an official and medics said, killing at least one and wounding five before fleeing.

The attack came one day after at least 12 suspected al Qaeda militants and three government soldiers were killed in two separate clashes in southern Yemen, according to Yemeni security officials.

In Wednesday's assault, witnesses and a security official said the gunmen opened fire on the minibus while travelling on a main road in Aden as the intelligence officers headed to work. It was the latest in a series of attacks on security officers in southern Yemen.

Al Qaeda's fingerprints seem to be all over this incident, the official told Reuters. It's not the first time security forces have been victims of terrorist acts, he added.

The official said two of the wounded were in serious condition. The official had earlier reported that eight were killed or wounded in the attack.

The incident came amidst a power transition in which President Ali Abdullah Saleh handed over his power to his deputy after signing a Gulf-brokered peace deal meant to end ten months of mass protests against his 33-year rule.

The unrest has emboldened groups linked to al Qaeda's Yemen-based regional wing, which the United States has called the most dangerous branch of the militant network, to expand their hold over parts of the province of Abyan in southern Yemen.

Yemeni troops have been fighting to dislodge the militants from the provincial capital, Zinjibar, and the town of Jaar.

Neighbouring Saudi Arabia, the world's number one oil exporter, and the United States have long seen Saleh as a bulwark against the Islamist group's Yemen branch, which has claimed responsibility for operations that include a failed plot to blow up a U.S.-bound passenger plane in 2009.

Saleh's opponents have accused him of ceding territory to Islamists to bolster his assertion that his rule keeps al Qaeda in check.

Washington and Riyadh are keen for the Gulf-backed power transfer deal to work, fearing that a power vacuum in Yemen may give militants space to thrive near key oil and cargo shipping lanes in the Red Sea.

(Reporting by Mohammed Mukhashaf; Writing by Nour Merza; editing by Sami Aboudi)