India, Aug. 5 -- Millions of Shiite Muslims observed the annual Arbaeen pilgrimage on Tuesday in the Iraqi holy city of Karbala, under the shadow of ongoing regional tensions and fears of another round of escalation in the US-Iran war.

Arbaeen is held 40 days after Ashoura, which commemorates the killing of Imam Hussein, grandson of the Prophet Muhammad, and members of his family, at the Battle of Karbala in 680 AD. Karbala Gov Nasseif Jassim al-Khattabi said on Tuesday that more than 22 million people entered the city during the pilgrimage, including about 5 million non-Iraqi visitors as well as Iraqis from different regions of the country.

The event is considered one of the world's largest annual religious gatherings.

Among the highe...