Two suicide bombers blew themselves up near a mosque in southeastern Iran on Wednesday, killing at least 39 people at a Shiite mourning ceremony, state media reported.
The attack took place outside the Imam Hussein Mosque in the port city of Chahbahar, near the border with Pakistan, the official IRNA news agency said.
The bombers targeted a group of worshippers at a mourning ceremony a day before Ashoura, which commemorates the seventh century death of the Prophet Muhammad's grandson Hussein, one of Shiite Islam's most beloved saints.
Iran has seen a string of explosions in past months, including a blast at a military training base in October that killed and wounded several servicemen.
Several armed groups hostile to President Mahmoud Ahmadinejad's rule are active in Iran, including Kurdish separatists in the northwest, Baluch militants in the southeast and some Arabs in the southwest.
The area of Iran is home to an armed Sunni militant group, Jundallah, or Soldiers of God, which has waged sporadic attacks to fight alleged discrimination against the area's Sunni minority in overwhelmingly Shiite Iran.
An armed Sunni militant group called Jundallah, or Soldiers of God, claimed responsibility in a statement posted on its website. The group has carried out sporadic attacks in Iran's southeast to fight alleged discrimination against the area's Sunni minority in overwhelmingly Shiite Iran.
The group said Wednesday's attack was a second act of revenge for the execution of its leader, Abdulmalik Rigi, in June.
"This operation is a warning to the Iranian regime that it must end its interference in the religious affairs of the Sunnis, stop executions and release the prisoners," said the Internet statement. "Otherwise, martyrdom operations will continue with a stronger forcer."
One of the attackers detonated a bomb outside the mosque and the other struck from inside a crowd of worshippers, state TV reported.
Forensic official Fariborz Ayati put the number of dead at 39 and said they included three women and one newborn baby, IRNA reported.
Anonymous threats
Mahmoud Mozaffar, a senior Iranian Red Crescent Society official, said emergency services had been put on alert over the past few days because of anonymous threats, according to another news agency, ISNA.
In July, two suicide bombers blew themselves up at a mosque in the same province, Sistan-Baluchestan, killing at least 28 people. Jundallah said that attack was revenge for the execution of its leader, Abdulmalik Rigi, in June.
That strike in the provincial capital, Zahedan, also targeted Shiite worshippers during a holiday, the birthday of Hussein, the prophet's grandson.
Iranian officials claim Jundallah, which has operated from bases in Pakistan, receives support from Western powers, including the United States. Washington denies any links to the group, and in November the State Department added Jundallah to a U.S. list of foreign terrorist organizations.
The group has also targeted members of Iran's Revolutionary Guard, the country's most powerful military force.
In its deadliest attack, a suicide bomber hit a meeting between Guard commanders and Shiite and Sunni tribal leaders in the border town of Pishin in October 2009, killing 42 people, including 15 Guard members.
Drug traffickers and smugglers also are active along the barren frontier area of Iran, Pakistan and Afghanistan and have launched attacks on security forces.