Security personnel defused a homemade bomb found on an aircraft during a domestic flight in Iran late on Saturday, Iranian media said.

The device was defused after the Tehran-bound Kish Air aircraft with 131 passengers on board made an emergency landing in the southwestern city of Ahvaz, the semi-official Fars news agency reported.

The incident occurred less than two weeks before the Islamic Republic holds a presidential election in which the conservative incumbent, Mahmoud Ahmadinejad, faces a challenge from reformers.

"Minutes after the ... Kish Air flight took off with 131 passengers from Ahvaz to Tehran, security personnel found a homemade bomb" on board, Fars reported.

Fars gave no further details about the incident, which was also reported by state radio.

The official IRNA news agency, in a report which did not mention the explosive device, said there had been a plot against the flight but that those behind it had been arrested.

"The plot ... was unsuccessful due to the security forces' awareness and those behind it were arrested," IRNA said.

Ahvaz is the capital of Khuzestan province, where many of Iran's oil fields are located. The province borders Iraq and is home to the mainly Shi'ite Muslim country's Arab minority.

On Thursday, a bombing in a popular Shi'ite mosque in the southeastern city of Zahedan killed 25 people and wounded more than 120. Three men convicted of involvement in the mosque bombing were executed in public on Saturday in Zahedan.

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 bombing, Saudi-owned Al Arabiya television said.

Thursday's bombing was the deadliest such incident in Iran since its 1980-88 war with Iraq. A blast in a mosque in the southern city of Shiraz killed 14 people in April last year but the country has otherwise been relatively peaceful.

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. - Reuters