Two students were killed and one seriously injured on Sunday when gunmen attacked a secondary school in northern Iraq, said a security official, dpa reported.
The unmasked gunmen used machine guns to attack the school in the town of Tikrit, some 170 kilometres north of the Iraqi capital Baghdad, added the official, who requested not to be named.
"The assailants escaped the school after the crime, the motive for which is not known yet," he said.
The attack was the second of its kind in the area in three months, according to the official.
Three students were killed in an attack on another school in January.
The rise in violence in Iraq in recent months has triggered security concerns after US troops completed their withdrawal from the country in December.
At least 27 people were killed Thursday in a series of apparently coordinated bombings in Iraq.