BAGHDAD, Iraq (CNN) -- Iraqi Shiite fighters who trained inside Iran to operate in assassination squads are starting to return home, the U.S. military told CNN.
"We are beginning to see indications that some 'special group' members are returning to Iraq and may be planning assassinations of key [Iraqi] government and security officials, as well as coalition forces," a U.S. military spokesman said.
The U.S. military uses the term "special groups" to describe Iranian-backed militias operating in Iraq.
In Baghdad, U.S. forces have distributed fliers featuring pictures of wanted "special groups" militiamen and offering rewards for tips that lead to arrests, residents say.
On the backs of the fliers are an image of handcuffs and an Arabic message that reads: "Welcome back -- We have been waiting for you."
Last month, the U.S. military said the assassination training was being conducted by Iran's Quds force and elements of Lebanese Hezbollah at four locations inside Iran: Qom, Tehran, Ahvaz and Mashhad.
The militiamen were trained for four months on subjects such as small arms and weapons training, reconnaissance, terrorist cell operations, sniper techniques, improvised explosive devices and rocket-propelled grenades -- including the RPG-29, a signature weapon of Lebanese Hezbollah and the Quds force, the military spokesman said.
The United States believes many of the Shiite fighters fled Iraq during a U.S. and Iraqi security crackdown this year.
CNN's Jomana Karadsheh in Baghdad contributed to this report