Two pig's heads were found Thursday attached to the fence of the Moroccan ambassador's residence in a chic suburb of the French capital, police said.
"The pig's heads were discovered by security staff on Thursday at 9:00 am. The ambassador was present," a police source told AFP.
The embassy, situated in Neuilly-sur-Seine to the west of Paris, has filed a formal complaint to police.
"We don't want to interpret this act, it's up to the authorities to investigate," an embassy official said.
Anouar Kbibech, head of the French Council for the Muslim Faith (CFCM) and the Morocco-linked Group of Muslims in France (RMF), said there was an "unhealthy atmosphere" in France "in which Muslims are the target of acts of stigmatization".
"The attack on the ambassador's residence shows that this provocation has moved up a level," Kbibech said.
"This latest desecration is aimed at the embassy of a country which is an ally of France, engaged in the prevention of radicalization and the fight against terrorism," he added.
Pig's heads have been left outside mosques in several French cities in recent years and a rise in anti-Muslim acts was recorded in the wake of the gun and suicide attacks on Paris in November last year which left 130 dead.