Muslim pilgrims continue their march on the Iraqi holy city of Karbala to commemorate Arba’een, the 40th day after the martyrdom anniversary of Imam Hussein, the third Shia Imam.

Arba’een, an annual Shia pilgrimage, is known as the world’s largest public gathering.

Here is a selection of pictures from the mass march:

(Photo by Tasnim news agency)

(Photo by Tasnim news agency)

(Photo by Mehr news agency)

(Photo by Mehr news agency)

(Photo by Tasnim news agency)

(Photo by Mehr news agency)

(Photo by IRIB News Agency)

(Photo by Tasnim news agency)

(Photo by IRIB News Agency)

(Photo by Tasnim news agency)

(Photo by IRNA)

(Photo by Tasnim news agency)

(Photo by Tasnim news agency)