Seven militants killed in Yemen clashes ADEN, Yemen (Reuters) - At least seven militants linked to al Qaeda were killed in clashes in Yemen's restive south, a regional tribal spokesman said on Saturday, as the impoverished Arab state fights to tame a stubborn insurgency. Yemen has launched an offensive against Islamist insurgents in the territory who took advantage of the chaos surrounding more than a year of mass protests and fighting that unseated Ali Abdullah Saleh from the presidency. Ali Aidah, spokesman for an army-allied tribal force, said five militants from Ansar al-Sharia, an al Qaeda-affiliated group, were killed in an ambush by tribesmen in the al-Arkoub area near the southern city of Lawder on Friday night. Two more militants were killed in an attack by tribesmen in another area outside of Lawder, he said. Separately, a security official in the southern province of Lahej said a Yemeni intelligence officer, Colonel Yasser Abdul-Qawi, was shot dead by unknown gunmen on Saturday morning while he was walking near the main city hospital. More than 250 people have been killed since government forces stepped up attacks on the militants whom it accused of assaulting a military camp near Lawdar earlier this month. Islamist insurgents have already taken control of a number of cities in the southern territory, which is close to key shipping lanes in the Red Sea. Yemen's new president, Abd-Rabbu Mansour Hadi, who took office vowing to fight al Qaeda, is also facing challenges from Shi'ite Muslim rebels in the north and secessionists in the south of the impoverished Arabian Peninsula state. Reporting by Mohammed Mukhashaf in Aden; Writing by Rania El Gamal; Editing by Mark Heinrich