Wathiq al-Hashimi, head of the Iraqi Group for Strategic Studies, said the insurgents are trying to push rival militias in a civil war, The Washington Post reported Wednesday.
"They are not arbitrary attacks. They are sending messages that security is not under control," he told the newspaper.
An official in Iraq's Interior Ministry said 327 Iraqis have been killed in explosions or assassinations since the departure of U.S. troops last month. About 2,640 Iraqis died in violence last year, Iraqi figures from the Interior and Health ministries indicated.
A senior White House official said a similar increase in violence occurred when U.S. troops left Iraqi cities in 2009.
"It's always a mistake to look at these things in the isolation of one or two weeks," the official said to the Post. He warned, however, that Iraqi leaders need to "reel back in" the political turmoil so that insurgents "don't have anything to use" in promoting sectarian strife, the newspaper said.