Suicide bombings in Iraq killed at least 36 people on Thursday in attacks targeting Shi’ite pilgrims ahead of a major holy day next week, police said.

Two years after U.S. troops withdrew from Iraq, violence is at its highest level since 2006-7, when strife between Sunnis and Shi’ites killed tens of thousands of people.

The first major attack of the day came when a suicide bomber blew himself up near a funeral tent, killing at least 16 Shi’ite pilgrims and wounding 31 in southern Baghdad’s mainly Sunni neighborhood of Doura, police sources said.