baghdad 78,000 people could trap islamic state-held hawija northern iraq unite nations say tuesday security force push recapture town iraq start offensive sept. 21 seize hawija fell hand militants iraqi army collapse 2014 face islamic state offensive remain last militant-held town country north u.n. humanitarian spokesman jens laerke say number people flee fight increase 7,000 people first week operation 12,500 people 78,000 remain trap say iraqi security officials say militants prevent residents leave others afraid escape toward government force explosives might lay islamic state around town remain concern live well-being vulnerable civilians remind fight civilians must protect time allow safely leave hawija laerke say laerke say people expect flee fight areas around hawija next 24 48 hours security force push densely populate areas hawija north baghdad stretch land along syrian border west iraqi capital last stretch territory iraq still hand islamic state u.n. say 78,000 civilians could trap iraq 's hawija