According to Furat news, they left Mosul for Karbala on Wednesday.
Arbaeen comes 40 days after Ashura, the martyrdom anniversary of the third Shia Imam, Imam Hussein (AS).
Each year, a huge crowd of Shias, including Iranians, flock to Karbala, where the holy shrine of Imam Hussein (AS) is located, to perform mourning rites.
In the past few years, around 20 million pilgrims from all over the world took part in the mourning ceremonies in the Iraqi holy city marking Arbaeen.
This year, Arbaeen falls on Tuesday, October 30.
Mosul was occupied by the Daesh (ISIL or ISIS) terrorist group in 2014.
After three years of fighting, the Iraqi army and popular forces, known as Hashd al-Shaabi, liberated the city and put an end to the terrorists’ so-called caliphate.