Christian families have fled Mosul to take refuge in outlying villages
Iraqi PM Nouri Maliki has vowed to protect Christians in Mosul after 1,000 police were deployed in the wake of sectarian attacks in the northern city.
Mosul's provincial governor said hundreds of Christian families had fled the city in the past week to seek refuge in outlying villages.
Sunni militants have been blamed for the murders of 12 Christians over the past fortnight.
Pope Benedict XVI, speaking at the Vatican, condemned the bloodshed.
"I urge the perpetrators of violence to renounce these acts and join with their brothers and sisters to work together in building a civilization of love," the pontiff said.
After talks with Christian Iraqi officials, the Shia prime minister said in a statement: "We will take immediate action to resolve the problems and difficulties faced by Christians in Mosul."
An AFP correspondent said police had set up checkpoints at churches in Mosul's four largely Christian areas and were patrolling the streets on foot.
A major operation by the security forces aimed at displacing insurgents has been under way for months in Mosul, which is considered by US and Iraqi commanders as the last urban stronghold of al-Qaeda in Iraq.
But the BBC's Jim Muir in Baghdad says that, unlike similar campaigns in the Iraqi capital and Basra, the situation in Mosul seems to be getting worse.
There were estimated to be around 800,000 Christians in Iraq in 2003, when coalition forces invaded, but at least one-third of the community is believed to have fled abroad.