At least five people are known to have died in days of ethnic unrest in the Iranian province of Khuzestan.
Clashes between Iranian Arabs and the security forces broke out on Friday.
The unrest, which led to the arrest of 200 people, followed rumours the authorities planned to change the ethnic mix in the mainly Arab region.
Iran has suspended the operations of the Arabic TV channel al-Jazeera, pending investigation of allegations its reports exacerbated the violence.
It is unclear who circulated a forged letter calling for modifications to the ethnic composition of Khuzestan that incited the violence, says the BBC's Frances Harrison in Tehran.
The government denies having any such plans.
Some have suggested it might have been factional rivalry ahead of the presidential elections in eight weeks' time; others that it was an attempt from outside to destabilise Iran, our correspondent adds.
The letter contained rumours that there was going to be an attempt to force Iranian Arabs to emigrate and to change the ethnic composition of the area which borders Iraq.
In Khuzestan, ethnic Arabs smashed and set fire to police cars, banks and government offices, while the security forces responded with rubber bullets and teargas.
Many of those arrested are now reported to have been released.
Defence Minister Ali Shamkhani, an Arab-Iranian from Khuzestan, is visiting the area, as is a team from the parliament's national security commission.
MPs are also collecting signatures for a petition urging the authorities to release any innocent detainees quickly, grant compensation to the victims and encouraging the security forces to show restraint.
Iran's Arabs, who are the majority in Khuzestan's capital Ahwaz, make up only 3% of the population of Iran.
Earlier, al-Jazeera said it was disappointed over Iran's move to suspend its operations and urged the authorities to reconsider their decision.
The channel described Iran's action as "surprising and unjustified".
It said it would maintain its "editorial policy of airing the full range of opinions and covering current affairs in Iran objectively and fairly".
The network - which is popular among Iranian Arabs - is reported to have been the first to broadcast news of the demonstrations.
The government is launching an investigation into al-Jazeera's coverage of the rioting.
Iranian MPs have criticised al-Jazeera, saying it portrayed the violence as a separatist unrest.