An Iranian airliner was forced to return to a southern airport minutes after takeoff because of a suspicious package on board, an incident a security official called a "sabotage operation."

The contents of the package were still being investigated, said air guards chief Mohammad Hasan Kazemi, according to a report by the official news agency IRNA on Sunday. The incident took place late Saturday night.

As Iran prepares for its June 12 presidential election, there have been a number of violent incidents. A bombing Thursday at a mosque in another southern city of Zahedan killed 25 people and wounded 80. A day later, a shooting at President Mahmoud Ahmadinejad's campaign office in the same city injured three people.

Kazemi left open the possibility of a link between those two incidents and the package on the airliner. He said "enemies" were trying to create a sense of hopelessness among Iranians before the election.

The plane, carrying 140 passengers, returned to an airport in the southwestern city of Ahvaz 15 minutes after takeoff Saturday after a passenger reported a suspicious package. The plane belongs to one of Iran's commercial airlines, Kish Air.

The flight was from Ahvaz to the capital, Tehran, about 500 miles to the northeast.