A Yemeni security official said gunmen have opened fire on a bus carrying intelligence officers and soldiers in the south of the country, killing one and injuring seven. The official said the attack took place early Wednesday in the port city of Aden. Security forces sealed off roads surrounding the site of the ambush. The official said it was not clear who carried out the shooting, but that it bore the fingerprints of al-Qaeda-linked militants. The official spoke on condition of anonymity because he was not authorized to talk to the press. Clashes take place almost daily in southern Yemen, where militants have overrun swaths of territory, taking advantage of the security vacuum resulting from the political unrest roiling the fragile and impoverished country.