Millions of Shia Muslims are gathering at shrines and mosques for Ashura, which falls on the tenth day of the holy month of Muharram. The festival commemorates the slaying of Prophet Muhammad's grandson Hussein at the battle of Kerbala, now in southern Iraq, in AD 680.

Shias beat their heads and chests with chains and knives, and gash their heads with swords to show their grief and echo the suffering of Imam Hussein.

Ashura 2015
Iraqi Muslims take part in a ceremony commemorating Ashura in the Shia holy city of KarbalaMohammed Sawaf/AFP
Ashura 2015
Men sharpen blades to be used for self-flagellation rituals during Ashura, at a shop in Lahore, PakistanMohson Raza/Reuters
Ashura 2015
Shia Muslims flagellate themselves with chains during an Ashura procession in Kabul, AfghanistanOmar Sobhani/Reuters
Ashura 2015
Bloody knives are seen as an Afghan Shia Muslim flagellates himself during an Ashura procession in KabulOmar Sobhani/Reuters
Ashura 2015
A child beats his chest while taking part in a procession in Islamabad, PakistanFaisal Mahmood/Reuters
Ashura 2015
A man arranges knives to be used by Shi'ite Muslims to gash their heads during a commemoration for Ashura in Kerbala, IraqAlaa al-Marjani/Reuters
Ashura 2015
A Pakistani Shia Muslim devotee uses chains to beat himself in LahoreArif Ali/AFP
Ashura 2015
Shia Muslim men beat their chests in Arbil, the capital of the autonomous Kurdish region of northern IraqSafin Hamed/AFP
Ashura 2015
Shia Muslim men flog their backs with knives on chains during an Ashura procession in Lahore, PakistanArif Ali/AFP
Ashura 2015
A Kashmiri Shia Muslim devotee bleeds as he holds knives during an Ashura procession in SrinagarTauseef Mustafa/AFP
Ashura 2015
Shia Muslim men beat their chests during an Ashura procession in Istanbul, TurkeyMurad Sezer/Reuters
Ashura 2015
Shia Muslim women shout Islamic slogans as they mourn during an Ashura procession in Istanbul, TurkeyMurad Sezer/Reuters
Ashura 2015
Shia Muslims walk on hot coals during the Ashura festival at a mosque in Yangon, MyanmarSoe Zeya Tun/Reuters
Ashura 2015
Shia Muslims perform with fire during a traditional mourning event in the holy city of Najaf, IraqHaidar Hamdani/AFP
Ashura 2015
An Iraqi Shia performs during the reenactment of the Battle of Karbala in Baghdad's northern district of KadhimiyaAhmad al-Rubaye/AFP
Ashura 2015
An Iraqi Shia girl takes part in an Ashura parade in Baghdad's northern district of KadhimiyaAhmad al-Rubaye/AFP
Ashura 2015
A child takes part in an Ashura ceremony in the village of Sanabis, BahrainMohammed al-Shaikh/AFP
Ashura 2015
A Bahraini Shia Muslim man poses for a picture during a ceremony commemorating Ashura in the village of Sanabis, west of ManamaMohammed al-Shaikh/AFP
Ashura 2015
Blood pours down a Shi'ite Muslim man's face after flagellating himself during a procession in Srinagar, KashmirDanish Ismail/Reuters
Ashura 2015
An Afghan Shi'ite Muslim man bleeds as he flagellates himself with chains during an Ashura procession in KabulOmar Sobhani/Reuters

This year the festival is marked during a particularly turbulent time in the Middle East, which has seen an increase in sectarian violence alongside the spread of the Islamic Sate and other extremist Sunni groups, who believe Shia Muslims are apostates deserving death.