Oil is king in Iran's economy. 

So when unrest broke out in recent days in the country's key western oil-producing areas — including Khuzestan province — it sent a deep shudder through the Iranian regime. More than 80 percent of Iran's oil and gas reserves originate in Khuzestan.

"If you go in and you crush that population, and then further inflame the situation and protests somehow debilitate Iran's oil production or disrupt Iran's ability to produce oil, that's deeply detrimental to the regime's pocketbooks," says the Carnegie Endowment's Karim Sadjadpour. "It was the oil strikes in 1978 which helped bring down the Shah of Iran."

Many towns and provinces in western Iran are ethnically and religiously diverse, including many with large Kurdish populations and others with Arab minorities.