An explosion in a mosque killed 15 people near Iran's volatile border with Pakistan and Afghanistan on Thursday and a local official said it was a terrorist attack.

The blast went off in Zahedan, the capital of a lawless province that frequently witnesses clashes between police and gangs involved in drug smuggling. It has also seen attacks by an Islamic militant group called Jundallah, which claims to be fighting for rights of Sunni Muslims in mainly Shiite Iran but is suspected of Al Qaeda links.

Alaeddin Mazari, a local journalist in Zahedan, told The Associated Press that the explosion occurred in the second biggest Shiite Muslim mosque in the city, some 1,000 miles southeast of the capital, Tehran.

Ali Mohammad Azad, the governor of Sistan-Baluchistan province where Zahedan is the capital, told the official Islamic Republic News Agency the explosion happened at 7:45 p.m. and said a terrorist was involved, but didn't provide further details. He told state television that he detained some suspects who planned additional attacks ahead of the June 12 presidential election.

The state news agency said 80 people were injured in the explosion and no group had taken responsibility. It 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, Jundallah, or God's Brigade, killed 11 members of the country's elite Revolutionary Guards in Zahedan.

Sectarian violence has been rare in other parts of Iran, but not totally absent.

Iran hanged three men last month for their involvement in a bombing inside a packed Shiite mosque in April 2008 that killed 14 people in the southern city of Shiraz, about 550 miles south of Tehran.

The blast went off as the mosque's cleric was delivering a weekly speech denouncing the Bahai faith and Wahabiism — an austere brand of Sunni Islam practiced mostly in Saudi Arabia, according to local news reports. Such speeches are not unusual in Iranian mosques.

Iran's Revolutionary Court said the three were members of the Iran Royal Association, a little known monarchist group that wants to overthrow the country's ruling Islamic establishment. It said they had ties to the U.S.

Tehran has repeatedly accused the U.S. and Britain of backing militants and opposition groups. Both countries deny it.