With this in mind it's no surprise that the population of 1.5 million Arabs living in Iran are under quite severe government repression. They are mostly found in the province of Khuzestan as well as along the coast across from the UAE, as can be seen on yet another ethnographic map of Iran. The majority are Shi'a, some having fled from Sunni oppression on the Arabian peninsula - although there is a large Sunni population along the coastal area which is another cause for tensions.
Khuzestan (Ahwaz in Arabic) is the most oil-rich region in Iran, but the Arab locals rarely receive any benefits from this and at most are employed as manual labourers on minuscule wages and terrible working conditions. This is a cause of anger for many who want more control over the natural wealth of their region, anger which was exacerbated under the centrist policies of Ahmedinejad and which led to several bombings of pipelines.
Khuzestan was also the goal of Saddam Hussein when he invaded in 1980. Iraq accused Iran of repression of the country's Arabs and tried to stoke up Arab nationalism within Iran, however, during the war the Khuzestani Arabs sided with the Islamic Republic, most likely due to religious reasons (Saddam was a Sunni and oppressed Shi'as in Iraq).
The Iranian state has also committed atrocities in dealing with peaceful protests carried out by Arabs, torturing, raping and executing dissenters. This is not uncommon throughout Iran, but it has an added dimension of collective punishment against an ethnic minority .
1- http://www.cidcm.umd.edu/mar/assessment.asp?groupId=63009, Analytic Summary, para. 3
2- http://www.cidcm.umd.edu/mar/assessment.asp?groupId=63009, Analytic Summary, para. 5
This is part of a series of posts on Iranian minorities, the other posts can be found here: Kurds, Baloch