PARIS — At a museum in eastern France, two men disguised with wigs used a sledgehammer and a hammer to smash a display case and make off with a 2,500-year-old gold necklace. The heist took under four minutes.

In a smash-and-grab at another French museum, three masked robbers stole 27 pieces of jewelry valued at more than 4.5 million euros (US$5.2 million), busting through two doors to break in.

Those thefts took place in July. This week, thieves sliced through a fence and climbed through the window of a museum on the French Riviera and fled with two paintings by Pierre-Auguste Renoir. They abandoned two other artworks by the Impressionist master as they made their escape.

The rash of the robberies, coming on the heels of last year’s stunning jewel heist in France’s most famous and most visited museum, the Louvre, show how the country is both blessed and cursed by its troves of treasure accumulated over centuries of conquest, creativity and having money to spend on art.

France’s passion for paintings, sculptures, ancient artifacts and other valuables and curios is a source of national pride and identity. Thousands of museums that house collections big and small help transmit France’s love of culture and history from one generation to the next. The biggest also draw millions of tourists who pump money into the French economy.

But keeping all that wealth safe is costly and difficult. Criminals see museums as soft targets. The brazen and agonizing theft of 88 million euros ($102 million) worth of crown jewels from display cases in the Louvre’s Apollo gallery served as a wake-up call. But it was only the most shocking example of broader threats to museums, and not just in France.

“When the jewels of a French king disappear, to be melted down because of the price of gold, it is tragic. It breaks everyone’s heart,” said Guillaume Poitrinal, president of a foundation that funds the renovation and protection of French cultural sites, the Fondation du patrimoine.

“We need to make it more difficult to steal works of art and objects that are part of France’s cultural heritage and belong to all French people. That is absolutely essential. And to achieve that, we need to invest,” he said in an interview with The Associated Press.

Before dawn Tuesday, two robbers made off with “Portrait of Madame Colonna Romano” and “Young Woman at the Well.” They dropped ’’Portrait of Madame Pichon” and “Coco Reading” as they fled through the garden of the Renoir Museum in Cagnes-sur-Mer.

They cut through a fence with an electric knife or saw and entered the museum through the ground floor, said Bryan Masson, mayor of the town between Cannes and Nice on the Mediterranean coast.

The heist took under three minutes. Masson estimated the artworks’ value at 9 million euros ($10.5 million). Offloading well-known, stolen art is impossible through legitimate channels, so the paintings could prove to be worth little or nothing for the thieves.

European police agency Europol says museum heists are becoming more violent, with sledgehammers, axes, crowbars and even explosives used for break-ins and to smash display cases.

Thieves also are increasingly targeting museum items with gold and other precious metals that can be melted down and with gemstones that can be removed and sold, the agency said in a report in August. Criminals believe “museum security measures are less robust than those in jewelry stores,” it said.

The ancient necklace stolen July 24 from the museum in Châtillon-sur-Seine, eastern France, was crafted from nearly half a kilo (a pound) of gold.

A record 10 burglaries targeted French and other European museums this summer, according to Jean-Christophe Castelain, director of Le Journal des Arts, a bimonthly revue of the art world.

“Eight of those 10 involved jewelry, coins or antique objects that can easily be melted down,” he said.

The Lalique Museum in Wingen-sur-Moder, further east near France’s border with Germany, has not reopened since the July 5 theft of jewelry there from six display cases busted open with sledgehammers and hammers. The public museum celebrates 19th-century jeweler and glassmaker René Lalique and his successors.

The pain is still raw for its director, Véronique Brumm Schaich. Her voice cracked with emotion during an interview. The museum is seeking 200,000 euros ($233,000) for security upgrades.

“Robbers’ tactics are evolving,” she said. “The recent examples show that we are not the only ones who need to go further in our efforts.”

Because of government budget squeezes, it’s not yet clear how much funding will come from public coffers, she said. The museum is also collecting private donations, because “these are things that are extremely expensive,” she said.

“These are difficult times,” she said. “A burglary never comes at a good time, but this one came at an especially bad time.”

Some of the funding that the Fondation du patrimoine provides, including for museums, comes from a national lottery. To help boost museum revenues, the foundation is also launching a pass that will grant subscribers access to 500 museums, monuments and châteaux.

“France is a country where we love passing the buck,” said Poitrinal, the foundation president. “People say it is the state’s responsibility or the city’s responsibility. I say it’s quite simple: it is everyone’s responsibility.”

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Associated Press journalists Catherine Gaschka and Alex Turnbull in Paris contributed.