Six security guards and 30 inmates were killed in a mass escape from a prison in northern Iraq, a senior security official said on Saturday.Forty prisoners, including nine charged with terrorism, escaped from the Khalis prison in the province of Diyala, around 75 kilometres north-east of the capital Baghdad, Interior Ministry spokesman Saad Maan said.He added that fighting erupted overnight inside the prison after inmates seized weapons from guards."Police are now hunting for the escapees in the nearby areas and have published their pictures for identification," Maan said.The escape followed three car bombs targeting the prison, media reported.Government forces, backed by local paramilitaries and a US-backed military coalition, are engaged in fighting to dislodge the Islamic State militant group from mostly Sunni areas in northern and western Iraq.The radical Sunni militia also controls large territory of neighbouring Syria.