A wave of car bomb blasts tore through Shiite areas south of Baghdad on Monday, killing at least 36 people and deepening fears that Iraq is rapidly spiraling back out of control.

The attacks capped a week of turmoil that is posing the greatest challenge to Iraq’s stability since U.S. troops left the country in late 2011. At least 218 people have been killed in attacks and battles between gunmen and security forces that began last Tuesday with clashes at a Sunni protest camp in northern Iraq.

The unrest follows four months of widespread protests by the country’s Sunni minority, whose members feel they are discriminated against and marginalized by Prime Minister Nouri al-Maliki’s Shiite-led government.

Officials fear that Sunni feelings of disenfranchisement could be exploited by extremist groups such as al-Qaeda in Iraq and militant organizations such as the Naqshbandi Army, which is tied to Saddam Hussein’s former regime.

In a possible sign of mounting worries about the deteriorating security, Iraqi authorities announced that they plan to close the country’s only border crossing with Jordan, starting Tuesday. The Interior Ministry said the move is related Iraq’s domestic affairs.

The route to the border runs through the cities of Ramadi and Fallujah, west of Baghdad, which have been hotbeds of Sunni anger at the government. Many Sunnis in western Iraq have economic, tribal and cultural ties with Jordanians, most of whom also are Sunni.

Sheik Fakhir al-Kubaisi, a protest organizer in Iraq’s Anbar province, criticized the closure plan as “another escalation by the Iraqi government to punish the revolting Iraqi people.” He predicted that the border closing would drive up the prices of food and medicine and might be tied to a coming security crackdown on protest sites in the area.

Lt. Col. Saad Maan Ibrahim, a spokesman for the Interior Ministry, insisted that the border move is solely a technical matter and is unrelated to the prevailing tensions in the country. He did not elaborate, but he said the crossing should reopen within 48 hours.

Iraq temporarily shut the same crossing in January, weeks after anti-government demonstrations erupted along the desert highway heading to the checkpoint.

The International Crisis Group, a nongovernmental organization, recently warned that the standoff between Sunnis and the central government has begun a dangerous slide toward confrontation.

Civilians and security forces gather at the scene of a car bomb attack in the southern Shiite city of Karbala, 50 miles (80 kilometers) south of Baghdad, Iraq, Monday, April. 29, 2013. (STR/AP)

— Associated Press