The 28th day of Safar, the second month of the lunar Hijri calendar, marks the passing of Prophet Muhammad (PBUH) and the martyrdom of Imam Hassan (AS).
Millions of devotees of the Prophet and the Ahl al-Bayt from across Iran, along with large numbers of foreign pilgrims, have traveled to the northeastern holy city of Mashhad to commemorate the solemn occasion.
Mourners gathered at the holy shrine of Imam Reza (AS), the eighth Imam of Shiite Muslims, to pay tribute to the Prophet and Imam Hassan and participate in mourning rituals.
Many of the pilgrims are expected to remain in Mashhad through Thursday to commemorate the martyrdom anniversary of Imam Reza (AS). They will gather at his holy shrine, as well as mosques and other religious centers across the city, for mourning ceremonies.