The 28th day of the month of Safar (the second month in the lunar calendar) marks the passing away of Islam's Prophet and Imam Hassan, presstv.ir reported.
The black-clad faithful gather in mosques, places of worship and religious sites to listen to eulogies delivered in honor of the revered figures.
Prophet Muhammad was born in about 570 AD in the holy city of Mecca. He received his first revelation and was chosen as Allah’s final messenger at the age of 40. He passed away at the age of 63 after 23 years of disseminating the message of Islam.
Thursday also marks the martyrdom anniversary of Imam Reza (PBUH), the eighth Shia Imam.
In the run-up to the occasion, thousands of Shia and Sunni pilgrims have been traveling on foot to the northeastern Iranian city of Mashhad to attend mourning rituals at Imam Reza’s holy shrine.
Memorial services are also organized in the cities of Qom, in central Iran, and Shiraz, in the southwest, which is home to the shrines of Imam Reza’s revered sister and one of his brothers, respectively.
The eighth Shia Imam was martyred after being poisoned by the Abbasid Caliph Ma’mun in the year 818 AD.