Mortar shells hit the courtyard of a girls' school in a mostly Sunni Arab neighbourhood of the capital, killing five pupils and wounding 20, while a US helicopter crashed during fierce fighting between Iraqi government forces and gunmen allegedly plotting to kill Shiite pilgrims and clerics during a religious festival.
The US military said two crewmen were killed in Sunday's crash, which occurred about 20 kilometres northeast of Najaf.
But the military statement did not give the type of aircraft nor say why it went down.
Some 300 militants were killed in the fighting, along with five Iraqi security forces, a provincial spokesman said on Monday, citing reports from officers at the site. The figure could not be independently confirmed.
Elsewhere, two car bombs exploded within a half hour in the northern city of Kirkuk, killing 11 people and wounding 34, police Brig Gen Sarhad Qader said.
Three ethnic groups -- Arabs, Kurds and Turkomen -- are in a bitter struggle for control of that oil-rich area.
The US command reported that three American military personnel were killed on Saturday -- one Marine in the Sunni insurgent stronghold of Anbar province and two army soldiers in the Baghdad area.
The mortar attack occurred about 11 am at the Kholoud Secondary School in the Adil neighborhood of west Baghdad, police and school officials said.
The principal, Fawzyaa Hatrosh Sawadi, said students were mingling in the courtyard during a break in exams when at least two shells exploded.
The blasts shattered windows in classrooms, spraying students with shards of glass.