BAGHDAD, April 6 (UPI) -- Five U.S. soldiers died in Iraq Sunday, including two soldiers killed when rockets landed in Baghdad's heavily fortified Green Zone, the military said.

In addition, as many as 22 Iraqis were killed in fighting between U.S.-led coalition forces and the militia of Shiite cleric Moqtada Sadr, the Los Angeles Times reported. At least 52 people were injured in the battles that broke out Saturday night in Baghdad's Sadr City, CNN and KUNA reported, while the Times said hospital sources pegged the number of wounded at 96.

Besides the two soldiers killed in the Green Zone, one soldier was killed in an attack on the Rustamiyah base in eastern Baghdad and one was killed in a roadside bombing in Diyala province. At least 31 more people were wounded in the attacks, the military said. A fifth soldier died in a non-combat incident, the Times reported.

All exits and entrances to Baghdad were placed on lockdown, with U.S. and Iraqi snipers on building tops and helicopters hovering over the city. The fighting occurred just after the Iraqi government called on Sadr to disband his Mahdi Army.

Meanwhile, a busload of 42 college students was captured by militants outside Mosul Sunday, but they were released within hours, a Mosul security forces spokesman said. Four people in a second bus were injured.