An unknown group has claimed responsibility for a Qatar suicide bombing that killed a Briton, and vowed to hit churches and “crusader” military bases in the region, an Internet statement posted on Tuesday said. Qatar boosted security in the capital Doha as investigators hunted for clues of any al Qaeda involvement in Saturday’s attack, the first in the Gulf Arab state which hosts the U.S. Central Command that directed the 2003 invasion of Iraq. “We claim responsibility for the historic Qatar operation, carried out by a lion of the Army of the Levant,” the statement posted on a Web site used by Islamists said. Full Story