A manhunt is underway after thieves broke into the Renoir Museum on the French Riviera early on Tuesday and stole several paintings worth an estimated €9 million, the local mayor said.

Two people broke into the museum shortly before 6am ​and took ⁠four works of art, dropping one as they left, Cagnes-sur-Mer mayor Bryan Masson announced on social media.

“Attacking the Renoir museum is attacking a part of the history and heritage of Cagnes-sur-Mer. These actions are particularly serious,” Masson said in his message.

Local outlet Nice-Matin identified the stolen paintings as the Portrait of Madame Pichon (1895); Portrait of Madame Colonna Romano (1910); Coco Lisant (1905); and Jeune fille au puits (1886), all by the French impressionist Pierre-Auguste Renoir.

The heist comes just months after a raid on Paris’ famed Le Louvre art museum, making off with €88 million ($102.3 million) worth of jewels, including Empress Eugenie’s tiara.

Coco Lisant was looted by the Nazi regime during the Second World War and returned to France only in 1994.

The portrait of Madame Colonna Romano and ‘Jeune fille au puits’ were on loan from the Musée d’Orsay in Paris, according to the museum’s website.

The latest heist comes only weeks after Italian police recovered paintings by Renoir, Paul Cézanne and Henri Matisse that were stolen earlier this year from a private museum near the city of Parma.

The Italian Carabinieri’s art recovery squad said in August that they had recovered Renoir’s Fish, valued at $3.5million, among the artworks stolen in March.

Renoir’s most valuable works have fetched dozens of millions of dollars at auctions in the past.

The museum was created in 1960 in Renoir’s mansion on a hill in Cagnes-sur-Mer, near Nice, where he died in 1919.

The collection on display in the museum includes 13 paintings from the master and some 40 sculptures, furniture and photographs.

Art thieves in Europe are committing more violent robberies and specialist gangs have been replaced by ad hoc ​opportunists recruited through social media, pan-European police body Europol said last month.

In late July, two thieves posing as tourists stole two ‘priceless’ archaeological artifacts from the Musée du Pays Châtillonnais, south east of Paris.

Thieves also snatched around 20 pieces of jewelry valued at around $4.5million in total from the Musée Lalique in Wingen-sur-Moder over the summer.