The Islamic State branch known as ISIS-Khorasan, which US intelligence says appears responsible for the mass shooting attack near Moscow, poses the greatest Islamist extremist threat to security in Germany, its interior minister said on Tuesday. “The threat level is still high,” Nancy Faeser said in a statement. “It was already high before the attacks in Moscow and has remained consistently high.” She spoke four days aftercamouflage-clad gunmen opened fire with automatic weapons at concertgoers outside the Russian capital, killing at least 139 people and injuring 180 in an attack claimed by Is…