The PMU, also known as Hashd al-Shaabi, said in a statement that the operation includes setting up checkpoints and deploying forces in the southern parts of the city, al-Ahed News reported.
It added that it has been launched ahead of the martyrdom anniversary of Imam Hadi (AS), the 10th Shia Imam, which is marked on Monday.
The forces taking part in the operation have so far found and seized some equipment of Daesh terrorists, the statement said.
A large number of pilgrims visit Samarra on the third day of the lunar Hijri month of Rajab every year (falls on Monday, February 15, this year) to mourn the martyrdom anniversary of Imam Hadi (AS).
The holy shrine of the 11th Imam-- Imam Hassan Al-Askari (AS) – is also in Samarra.