A bomb explosion in the south-eastern Iranian city of Chabahar has killed at least 39 people, the official Iranian news agency says.
The suicide attack took place outside the Imam Hossein Mosque, Irna reported.
The militant Sunni Muslim group Jundullah claimed responsibility for the bombing.
The province of Sistan-Baluchistan is prone to unrest, with the mainly Sunni population often claiming discrimination by Shias.
The attack reportedly targeted pilgrims marking Ashura, the Shia mourning day.
A number of women and children are believed to be among the dead.
Many more people were injured.
Irna quoted the head of the Chabahar Security Council, Ali Bateni, as saying there were two attackers and one had been arrested.
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