A bomb blast at a Shiite mosque in the southeastern Iranian city of Zahedan killed at least 19 worshippers and wounded 80 others, the official IRNA news agency reported.
The evening explosion struck the Amir al-Momenin mosque in Zahedan, the restive capital of Sistan-Baluchestan province, which has a substantial Sunni minority, it said.
"The bomb exploded at the time of evening prayer and killed a number of worshippers," Ali Mohammad Azad, the governor general of the province bordering Pakistan and Afghanistan told reporters.
"It was a terrorist attack and the bomb was exploded by a terrorist," Azad told reporters, according to IRNA.
Fars news agency reported that 20 people were killed in the bombing.
Azad said soon after the explosion "members of a terrorist group who wanted to get out of Zahedan were arrested."
"The members of the terrorist group intended to explode bombs in some other areas of Zahedan, but they have been arrested due to the efforts of the provincial intelligence office."
Azad said "bandits and terrorists intended to disturb the order in the province before the election considering the insecurity in the eastern neighbouring countries."
According to IRNA, Zahedan's Friday prayer leader Ayatollah Abbas Ali Soleymani told reporters that "one of the main persons involved (in the attack) had been arrested" and "he will soon be punished in front of the mosque."
Fars said the mosque is the second biggest Shiite mosque in Zahedan and also a "gathering place for revolutionary Shiites."
The agency said no group had so far claimed responsibility for the bombing, and that security and police services were in control of the area.
On February 18, Al-Gadhir mosque in Zahedan was attacked. A bomb apparently carried by a motorcyclist exploded but caused no casualties.
The last major attack in Zahedan was a February 2007 strike by suspected Sunni rebels that killed 13 elite Revolutionary Guards.
Thursday was a public holiday in Iran to mourn the death of Fatima Zahra, the daughter of the Prophet Mohammed.
The explosion comes just weeks ahead of Iran's June 12 presidential election.
Sistan-Baluchestan province has a large ethnic Baluch minority.
In recent years, it has been the scene of a deadly insurgency by Sunni rebels of the Jundullah (Soldiers of God) group which is strongly opposed to predominantly Shiite country's government.
The province also lies on a major narcotics-smuggling route from Afghanistan and Pakistan.
In April 2008, the bombing of a packed mosque in the southern city of Shiraz during evening prayers left 14 people dead.
|Blood stains the ground inside the Amir al-Momenin mosque following a bomb blast in the southeastern Iranian city of Zahedan.|
The strike in Shiraz was the first in decades in Iran's Persian heartland. The normally calm city is not in a border zone, nor is it home to any significant ethnic or religious minority population.
Iran has in the past blamed US and British agents based in neighbouring Iraq and Afghanistan for launching attacks on border provinces with significant ethnic minority populations.