They are to take part in mourning ceremonies in the Iraqi city of Karbala which hosts the holy shrine of Imam Hussein, the third Shiite Imam.
“The number of pilgrims who have crossed land and air borders [into] Iraq since September 30 has crossed the 2-million mark, and the figure is expected to cross 2.2 million today,” said Hossein Sajedinia, the deputy Iranian police chief for operations.
He said border exit points are overcrowded, but that people are smoothly crossing through the gates.
He urged pilgrims to use all three border exit points to prevent overcrowding at the Khosravi border checkpoint, which is a popular exit point for Iranians leaving the country.
Arbaeen, which is one of the largest religious gatherings in the world, comes 40 days after Ashura, the martyrdom anniversary of Imam Hussein (AS).
Each year, a huge crowd of people flock to Karbala, where the holy shrine of Imam Hussein is located, to perform mourning rites.