cairo three policemen one security guard civilian kill number people injure attack militants egypt north sinai province monday interior ministry say militants attack security post secure national bank egypt branch arish provincial capital explosives gun statement say egypt fight insurgency militants affiliate islamic state northern part sinai peninsula hundreds security force kill since 2013. attack security force common since islamist president mohamed mursi oust 2013 follow mass protest rule militants raid bank branch steal amount yet value statement say force search area perpetrators defuse explosives security source tell reuters three egyptian policemen one security guard three civilians kill 22 others injure attack witness say arm militants five cars fire security force near church nbe branch flee scene militants fire shots randomly street celebrate raise black flag islamic state roam streets 20 minutes disappear say alaa lotfy shop owner area witness clash least 24 militants six soldier kill sunday attack military outposts north sinai militants kill five attack egypt 's sinai interior ministry