* Incidents come as Iran prepares for election
* Commander says unrest in southeast prevented
By Fredrik Dahl
TEHRAN, June 1 Iran has arrested a number of people it accuses of sowing sectarian discord in a southeastern city where the bombing of a Shi'ite mosque killed 25 people last week, a senior commander was quoted as saying on Monday.
News of the detentions in the city of Zahedan, where many of Iran's minority Sunni Muslims live, came two days after security personnel defused a homemade bomb found on a flight bound for Tehran from a southwestern city, according to Iranian media.
Officials have blamed both Thursday's bombing and Saturday's plane incident on Iran's foes, with one saying they wanted to "create a security-threat environment" ahead of the mainly Shi'ite Muslim country's June 12 presidential election.
Conservative President Mahmoud Ahmadinejad, who often rails against Iran's Western enemies, faces a challenge in the vote from reformers seeking detente in its international relations.
Brigadier General Ahmad Reza Radan, deputy commander of Iran's security forces, said "a number of individuals who intended to create insecurity" in Zahedan had been detained.
Zahedan is the capital of Sistan-Baluchestan province, home to the Islamic Republic's mostly Sunni ethnic Baluchis. Near Pakistan, the region is scene of frequent clashes between security forces and heavily armed drug smugglers and bandits.
On Thursday, the bombing of a popular Shi'ite mosque in Zahedan killed 25 people and wounded more than 120.
Three men convicted of involvement in the bombing, the deadliest such incident in Iran since its 1980-88 war with Iraq, were executed in public on Saturday in the city.
SUNNI CLERIC "THREATENED"
"In the past days some people planned to sow discord between Shi'ite and Sunni citizens in the region. Fortunately, with the prompt presence of government officials and religious dignitaries, unrest was prevented," Radan said.
"Order and security have been restored in the city," Mehr News Agency quoted him as saying.
Sistan-Baluchestan governor Ali Mohammad Azad said a number of Sunni extremists had been "identified" and would face sentencing after the election, the ISNA news agency reported.
Mehr, a semi-official news agency, said special police were deployed throughout the city of roughly 600,000 people.
A Sunni opposition group named Jundollah (God's Soldiers), which Iran says is part of the Islamist al Qaeda network and backed by the United States, said it was behind the mosque bombing, Saudi-owned Al Arabiya television reported on Friday.
Iran has previously accused the United States, its arch-foe, of supporting Sunni rebels operating on its border with Pakistan. Jundollah says it fights for the rights of Iran's minority Sunni population.
A Sunni cleric in Zahedan, Friday prayer leader Molavi Abdolhamid, said he had received threats and his bodyguard was beaten after the bombing, the Etemad daily reported.
An Iranian official has said he could not confirm whether there was a connection between Saturday night's plane incident and the mosque bombing in Zahedan.
On Sunday, a Tehran theatre was evacuated after a bomb threat but police found nothing inside, ILNA news agency said. (Editing by Andrew Roche)