French authorities have launched a criminal probe after at least five pig heads were discovered Tuesday morning outside mosques in Paris and its suburbs, acts condemned as "abject" by police and officials amid rising concerns over religious tensions.

Paris police chief Laurent Nuñez announced the findings on X, stating that investigations were underway immediately to identify those responsible for what he called despicable provocations.

The discoveries, made as mosques opened for the day, included sites on Rue Marey in the 20th arrondissement, in front of a mosque in the 15th, inside a suitcase in the 18th, at the Islah mosque entrance in Montreuil (Seine-Saint-Denis), and another in Montrouge (Hauts-de-Seine).

One head bore the word "Macron" painted in blue, adding a political edge to the incident, according to police sources and the Paris prosecutor's office.

The Grand Mosque of Paris decried the events as a "sad stage" in anti-Muslim hatred, while locals near Rue Marey expressed shock at the disruption in their quiet, working-class neighborhood.

Interior Minister Bruno Retailleau voiced strong support for affected worshippers on X, calling the attacks "unfathomably cowardly" and vowing to pursue justice. "Attacking places of worship is unacceptable; we must not insult any religion," he told reporters.

Pig heads are a potent symbol of insult in Islam, where pork is forbidden, and similar desecrations have marred French mosques in the past - from a 2019 attack in Bergerac to earlier cases in Montauban and Castres tied to broader Islamophobia.

No claims of responsibility have emerged yet.