Muslims around the world are celebrating Ashura, the tenth day of Muharram, which is the first month of the Islamic calendar.
The word Ashura literally translates to "10", indicating the date of the holiday.
Some Shia Muslims observe the day to mourn the death of Hussein, the Prophet Muhammad's grandson, at the Battle of Karbala on Muharram 10, about 1,400 years ago.
In the Battle of Karbala, a small group led by Hussein, the grandson of Prophet Muhammad and the son of his companion Ali, was defeated and murdered by an army sent by Yazid I, the second leader of the Umayyad Dynasty - the first Muslim dynasty.
Sunni Muslims observe Ashura to commemorate three events: The day Noah was said to have left the Ark, the day Moses and his people were saved from the Pharaoh and the arrival of the Prophet Muhammad's migration from Mecca to Medina in AD 622.
Muslims voluntarily fast from sunrise to sunset on the day of Ashura, following the example of the Prophet Muhammad.