Cleric Sheik Nimr al-Nimr threatened to break away if Saudi authorities don't treat Shiites better. Followers of the sect make up 10 percent of the kingdom's population of 22.6 million and they have long complained of discrimination, saying they are barred from key positions in the military and government and are not given an equal share of the country's wealth.
"Our dignity has been pawned away, and if it is not ... restored, we will call for secession," al-Nimr said during Friday prayers last month. "Our dignity is more precious than the unity of this land."
Since that incendiary sermon, more than 35 people have been arrested in a government crackdown and al-Nimr has gone into hiding. Police have set up checkpoints on the roads leading into Awwamiya, one of the Shiite area's poorest towns.