Iranian mourners mark Arbaeen Day

As Shia Muslims celebrate Arbaeen Day, many in Tehran, who were unable to join the millions of pilgrims in Iraq, took to the streets of the capital to join them in spirit.

The Arbaeen pilgrimage is considered the largest annual public gathering in the world.

Each year, Arbaeen takes place 40 days after Ashura, the anniversary of Imam Hussein's death at the Battle of Karbala - in present-day Iraq - in the 7th century.

Hussein was considered by his followers to be the rightful heir to the Prophet's legacy.

When he refused to pledge allegiance to the Umayyad Caliphate, he was killed in the battle, cementing the schism between Sunni and Shia Islam