Millions of people from across the world are taking part in a march toward Iraq's holy city of Karbala to attend mourning rituals on Arbaeen, marking 40 days after martyrdom anniversary of the third Shia Imam.
Arba'een, which in Arabic means forty, falls on December 13 this year and marks 40 days after the anniversary of martyrdom of Imam Hussein (AS) the grandson of the Prophet Muhammad (PBUH).
The occasion marks the seventh century martyrdom of Prophet Muhammad's grandson, the Shiite saint Imam Hussein (PBUH).
The event has attracted more than one million from Iran.The Iranian Embassy in Iraq has announced that until December 7, some 1.1 million Iranians entered Iraq to attend the annual mourning rite.
The pilgrims show their commitment to the Shia imam by walking tens of miles barefoot.
Shiite Muslim pilgrims walk through a main road in Baghdad on their way to the shrine central city of Karbala.
The Iraqi Red Crescent society in Baghdad has put all its medical teams on alert to treat pilgrims who are walking by foot to Karbala - an 80 kilometre journey from the capital Baghdad and other routs like iran officials borders or airports like holy city of Najaf.
Iraqi troops have stepped up security as extremists have previously staged attacks on Shiites during Arbaeen festival.
Imam Hussein was martyred - along with approximately 70 followers - by an army of Umayyads during a battle in 680 AD.
The celebration of Arbaeen will reach its climax on Friday and Saturday when the pilgrims arrive in Karbala, where Imam Hussein and his half-brother Hazrat Abbas are buried.
A view of the Imam Hussein shrine and Imam Abbas shrine in the city of Karbala.
The shrine Iraq city of Karbala sees millions of visitors every year over the 40-day period of mourning that follows the annual commemoration of the death of Imam Hussein, who was slain by the forces of the Yazid in 680 AD.