"Our brother Abu Muawiya al-Falluji rammed a convoy for the 'United Nations waging war against Muslims' surrounded by heavy US protection," the group said in a statement.
The name given for the suicide attacker suggests he was an Iraqi from the insurgent stronghold of Fallujah, which lies around 40 kilometres west of Baghdad.
In its statement, IS claimed yesterday's attack had left many dead and alleged the Iraqi government had taken away the bodies of US personnel.
"The convoy was strictly a UN convoy, there was nobody who isn't UN staff," a press officer for the UN mission in Iraq said.
A police officer said three people were injured.
The UN press officer said the attack was the first in a long time against the United Nations, which pulled out of Iraq for several years after a devastating bombing against its Baghdad headquarters in August 2003.