Today is the 10th of Maharam, or Ashura (literally 10 in Arabic), a day of mourning for Shia Muslims. Shias believe that Hussein ibn Ali, the rightful successor of the prophet Mohammed (in their opinion), was martyred on this day in the 600s AC. Many Shia communities observe the day by dressing in black and retelling stories of Hussain's tragic and untimely death and how he was cheated from his rightful place as the leader of the Muslim community, or umma. Ashura is probably most famous for the images of Shia men, marching in streets beating their chests with their hands, chains and sometimes blades in mourning for Hussein.
When the Prophet Mohammed died, he did not leave a clear successor. At that time, it was common for leaders to be selected by the community - they did not inherit positions. However, some people claimed that the Prophet had in fact named Ali (Hussein's father and husband to the Prophet's wife) as his successor, while others said that the Prophet's father-in-law, Abu Bakr, was the one the Prophet intended to lead the Muslim people. In the end, Abu Bakr led both the Sunni and Shia communities. The name Shia, comes from Shia Ali, or the party of Ali (Hussein's father), and the split between Sunnis and Shias date back to this time.
Ashura tends to aggravate differences and tensions between Shia and Sunni communities. Extremist Sunnis believe celebrating Ashura is sacrilegious and have been known to attack Shias during their mourning processions. Saddam Hussein actually banned Ashura in Iraq for many years to avoid conflict.
In Afghanistan, the Hazara community is Shia, and they mourn the death of Hussein openly, despite their minority status. I live in a Hazara neighborhood, but I didn't get to see the procession because we were under 'lock down' today - just in case there was any trouble between the Sunni and Shia communities. The pictures above were taken two days before Ashura, and most of them are in my neighborhood in the south west part of the city, near the Parliament building.