Iran has suspended operations by the al-Jazeera television network, accusing it of inflaming violent protests by the country's Arab minority.
Three people have died in ethnic clashes in Iran's south-west Khuzestan province over the past few days.
The riots are thought to have been sparked by alleged plans - which the government denies - to change the area's ethnic makeup.
Al-Jazeera described the 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 television 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.
"If it is proved that al-Jazeera committed a crime, it will be prosecuted," Mohammad Khoshvaght of the culture and Islamic guidance ministry told state television.
Iranian MPs have criticised al-Jazeera, saying it portrayed the violence as a separatist unrest.
The Popular Democratic Front of Ahwazi Arabs in Iran, which is based in London, told al-Jazeera that it had called for peaceful demonstrations in Khuzestan to "to mark 80 years of Iranian occupation" but the government had opted to deploy military force.
Iran's Arabs, who are the majority in Khuzestan's capital Ahwaz, make up only 3% of the population of Iran.
Iran's interior ministry says the area is now calm.