An explosion in a mosque killed 15 people and wounded 50 others in southeast Iran near the Pakistani border, Iran's official news agency reported.
Thursday's report said officials were investigating the cause of the explosion in the Iranian city of Zahedan, some 1,000 miles (1,600 kilometers) southeast of Teheran.
The report quoted an unnamed official as saying part of the mosque was destroyed and rescue teams were transferring the bodies of the dead and injured.
In 2007, a bombing by the militant group Jundallah, or God's Brigade, said to have links to al-Qaida killed 11 members of Iran's Revolutionary Guards in Zahedan.
The area near the Pakistani border has also witnessed clashes between Iranian security forces and drug smugglers.