Seventeen Yemeni tribesmen were killed Thursday in clashes that followed the assassination of local Al-Qaeda leader by his half-brother in his stronghold southeast of Sanaa, tribal chiefs said. The clashes erupted after Tarek al-Dahab was shot dead by his half-brother Hizam in the town of Al-Masaneh, several tribal chiefs said, confirming that the killer and his brother Ahmed were among the 17 killed in the gunfights.