As Sunni militants surge towards Baghdad, a mass exodus tries to stay ahead.

Hundreds of thousands of Iraqis are fleeing the sweeping violence in the north of the country.

That's where Sunni rebels have overtaken government forces in just a matter of days, and effectively control major population centers.

Many of the displaced families are setting up tents at this camp, near Arbil.

They say rebels are setting up councils to run the towns they capture, one by one.

(SOUNDBITE) (Arabic) DISPLACED WOMAN, ALI AYMAN, SAYING:

"The situation is very quiet, and armed militants are deployed everywhere, and there was a cooperation between them and the people, but it is out of fear, not love. People are afraid of the calm before the storm."

The rebels want to set up a Sunni caliphate on both sides of the Iraq-Syria border.

In Tikrit, militants paraded dozens of captured government forces.

They packed them into trucks, their destination unclear.