ABDI SHEIKH ISLAMIST fighters set off a bomb and then stormed a government building in Somalia's capital, killing at least five civilians, the ministry of information said. Attackers from the al Shabaab group charged into the block that houses the office of Mogadishu's mayor around noon and got caught in a firefight with security forces, the ministry and witnesses said. Security killed six of the militants and cleared the area by about 6 p.m., the ministry said on its Facebook page. Al Shabaab has stepped up attacks in a show of resilience since President Hassan Sheikh Mohamud's government launched an…