The attack came in Mosul, the most dangerous city in Iraq.
Tens of thousands of Sadr’s Shiite supporters expressed solidarity with Iraqi security forces while demanding an end to the US occupation.
On a surprise visit that lasted less than five hours, the US president also met with Iraq's prime minister.
Disarmed by US forces in 2003, the 3,400 People’s Mujahideen members at Camp Ashraf have been asked to leave by the Iraqi government.
Gen. Raymond Odierno outlines the challenges facing US forces as they continue to tamp down violence while working toward a June deadline to withdraw from Iraqi cities.