Iraq’s Prime Minister Nuri al-Maliki Sunday slammed as criminal acts the displacement of Christian citizens by the Islamic State (IS) extremist group from northern Iraqi city of Mosul, calling for a worldwide unified stand against the militants.

A statement issued by Maliki’s office said the IS militant threat against the Christian minority in its seized areas “reveals without any doubt the extremist criminal and terrorist nature of this group, and the danger it represents to the humanity and its centuries-old heritage”, Xinhua reported.

“We call on the whole world to tighten the siege on them (IS militants) and to stand united to fight them,” the statement said.

The Iraqi prime minister’s comments came in the wake of hundreds of Christian families fleeing their homes in militant-held Mosul Saturday fearing an ultimatum to accept extremist militants’ options.

The self-proclaimed caliph of the Muslims Abu Bakr al-Baghdadi granted the Christians another option, which is to leave the militant-seized city by themselves without their properties by the deadline of Saturday noon, according to the statement.

The crisis in Iraq has taken a turn for the worse since June 10, when Sunni insurgent groups took control of Mosul, the second largest city, and then progressed to other areas in the north and centre of the country.

The IS, formerly known as the Islamic State of Iraq and Greater Syria (ISIS), June 29 proclaimed an Islamic caliphate extending from the Syrian province of Aleppo to Diyala in Iraq, a measure which was rejected by other rebel groups in both countries.