The mausoleums of Imam Hadi (AS) and Imam Hassan Askari (AS) in the city have been covered in black on the sad occasion.
Implementing special plans has started in Samarra and on the roads leading to the city to ensure security and serve the pilgrims.
They include setting up more than 250 Moukebs (resting places with special facilities and services) on the roads leading to Samarra.
Also, more than 3,500 forces and 600 military vehicles have been deployed by the Popular Mobilization Units (PMU) to safeguard security.
Pilgrims also receive health and medical services during their visit to the holy city.
Shia Muslims all over the world mourn the martyrdom anniversary of Imam Hadi (AS) on Saturday, which marks the 3rd day of the lunar Hijri month of Rajab.