Ashura is observed on the tenth day of Muharram, the first month of the Islamic lunar calendar, by all Muslims, and it marks the day Nuh (Noah) left the Ark and the day Musa (Moses) was saved from the pharaoh of Egypt by God.

The Prophet Muhammad used to fast on Ashura, a common tradition commemorated by Sunni Muslims.

For Shia Muslims, the day also commemorates the 7th-century martyrdom of Hussein, Prophet Muhammad’s grandson, in the Battle of Karbala.

To mourn his death in the year 680, Shia worshippers, wearing black, cry and beat their chests in unison and some flagellate themselves with swords and knife-edged chains.

More than 1,340 years after Hussein’s martyrdom, Baghdad, Tehran, Islamabad and other major cities were adorned with symbols of Shia piety and repentance: red flags for Hussein’s blood, symbolic black funeral tents and black dress for mourning, processions of men and boys expressing fervour in the ritual of chest beating and self-flagellation with chains.

In Afghanistan and Pakistan, authorities cut mobile phone services in key cities holding commemorations for fear of bombings. Internet monitoring group NetBlocks confirmed on Monday that Afghanistan was experiencing significant service disruptions.

In Iran, thousands of men and women shrouded in black thronged the streets of the capital Tehran.

Green plumage fluttered in the air. Camels covered with multi-coloured cloth paraded through the city, evoking how Hussein set out from Mecca with a small band of companions. Iranians pounded their chests in mourning and chanted in unison, while some mourners clad in black wept.

In Iraq, black flags of grief fluttered over the capital’s major thoroughfares.