There are reports of violence in the western city of Ahvaz in Iran's Khuzestan province, where according to the Human Rights Activists News Agency, 15 people have been killed and dozens have been injured and detained.
Al-Arabiya TV also has a brief report.
Friday's crackdowns by Iranian security forces came during a protest (dubbed the "Ahvaz Day of Rage") meant to mark incidents that took place in Ahvaz in 2005, when the ethnic Arab population staged rallies against the Iranian government over what they said were systematic injustices and discrimination.
On the April 15, 2005 protest, 360 people were reported to have been arrested. On June 12 of the same year, a series of bombs exploded in the Ministry of Housing, in front of the governor's house and in the Office of Civil Engineering in the provincial capital.
At the time, the Islamic Republic News Agency reported two deaths.
Following the attack, Al Jazeera reported on the long history of grievances held among the Arab Ahvazis:
Two weeks before Sunday's attacks, the director of the Ahvaz Education and Human Rights Foundation told the UN Sub-Commission on the Promotion and Protection of Human Rights that Tehran needed to address basic issues.
Khalid Abdian alleged that the government continues ethnic restructuring, confiscation of Arab land and forced displacement of Ahvazi.
"We are being perceived as disloyal, suspicious and a security risk - who some day may reclaim the oil-rich land of Khuzestan," he said.
"The policy of the Islamic republic, like its predecessor, is directed at the eradication of the national identity and forceful assimilation of Ahwazi Arabs, and to a lesser degree, other nationalities such as the Turks, Kurds, Baluchis and Turkmen.
A series of four more attacks hit Ahvaz between 2005 and 2006, when Iranian officials arrested nine men, all of whom were shown confessing to having ties to groups outside Iran that wanted to cause instability within the country. At least four of those men were hanged in 2006.
The government in the past has accused the protests and attacks as being perpetrated by "Arab separatists".