CHICAGO: Two air rifle shots struck the outer wall of a mosque and Muslim education centre outside Chicago overnight, the Council on American-Islamic Relations said Sunday.
The shots were heard by worshippers who were outside the mosque and were powerful enough to damage the building's brick wall, it added.
The shots were allegedly fired by a neighbour with a history of opposition to the mosque, said the Chicago chapter of CAIR, the United States' largest Muslim civil rights and advocacy group.
Morton Grove police, the Federal Bureau of Investigation and the US attorney's office are investigating the incident.
"This is obviously an alarming situation that all parties are taking very seriously," CAIR-Chicago Executive Director Ahmed Rehab said in a statement.
"The weapon allegedly used in this incident is powerful enough to kill, and the projectiles reportedly came within inches of the head of the security guard on duty.