BAGHDAD — At least 20 people were killed by a series of car bombs in mainly Shiite districts of the Iraqi capital, Baghdad, on Monday and 11 others were killed by attacks in the southern city of Basra, police and medics said.

Scores of people have been killed in attacks over the past week as tensions between minority Sunni Muslims and Shiites who now lead Iraq have reached their highest level since U.S. troops pulled out in December 2011.

Eight car bombs in mainly Shiite districts of the Iraqi capital, Baghdad, killed at least 20 people on Monday, police and medics said.

Two car bombs hit Basra, a predominantly Shiite southern city 420 kilometers (260 miles) southeast of Baghdad. The first struck the Hananiya neighborhood, near a busy market and restaurants, and the second was detonated inside a bus terminal in Saad Square, police and medics said. Eleven people were killed.

More than 700 people were killed in April by a U.N. count, the highest figure in almost five years. Relations are coming under more strain by the day from the increasingly sectarian conflict in neighboring Syria.

Minority Sunnis, embittered by Shi'ite dominance since the overthrow of Saddam Hussein by U.S.-led forces in 2003, have also been staging street protests against Shiite Prime Minister Nouri al-Maliki since December.