In a statement, a spokesman for Asaib Ahl al-Haq group said it spotted new U.S. troop deployments in the country, threatening to target the forces if the Iraqi government and parliament failed to act.
On Saturday, images of Brig. Gen. Austin Renforth, Director of Joint Operations-Iraq for the Combined Joint Task Force, while touring the culture-rich Mutanabi Street in central Baghdad have triggered uproar across Iraq.
Renforth was pictured on the tour along with Baghdad's commander of operations Jalil al-Rubaie on the anniversary of the U.S. troop withdrawal from Iraq.
"The touring of General Austin in Baghdad streets is considered a blatant violation to state sovereignty," Jawad al-Talebawi, a spokesman for the group, said.
He went on saying that the group is closely monitoring the U.S. army's "illegitimate" movements and deployments across the country.
Al-Talibawi threatened that if the Iraqi diplomacy failed to declare a firm position, they would stand "in the face of the U.S. presence and its direct and indirect occupation of parts of the country”.
The Iraqi government has yet to comment on the statement.
U.S. troops ended their combat operations in Iraq in 2010, and focused their work there on training the Iraqi forces.
The last U.S. soldier left Iraq on Dec. 18, 2011, with the exception of a number of U.S. military personnel who remained under the authority of the U.S. Embassy.