When thieves broke into a French museum earlier this week and stole four paintings by the impressionist artist Pierre-Auguste Renoir, worth millions of euros, not everyone was surprised.

Just last month, the European policing agency (Europol) had warned that museum thefts across Europe were growing increasingly brazen.

And just days before the Renoir heist, internationally known art detective Arthur Brand predicted to the BBC that more high-profile burglaries were likely – particularly in the wake of the successful robbery at the Louvre in Paris last October.

The audacious crime in one of the world’s most famous museums stunned France, and the stolen jewellery worth €88m (£75m) has still not been recovered, nearly a year on.

“We will see more of this,” says Brand, “because if you are able to hit the Louvre, thieves all around the world are watching that, thinking, ‘Wow’ – and then they think, ‘Don’t we have a local museum with gold and silver?'”.

Within hours of the Louvre burglary, thieves had raided coins from a smaller museum in France. Since then, criminals have stolen a diamond necklace in Vienna, Bronze Age artefacts in Spain, and art from two Italian museums – and that’s only what the BBC has written about.

The heist at the Renoir Museum in Cagnes-sur-Mer is the latest, and detectives are still working to track down the remaining multi-million-pound paintings – two of which were quickly recovered after thieves dropped them in the museum garden.

Europol tells the BBC the number of museum theft cases reported to them across Europe began to increase about two years ago.

Its recent report says both the methods and targets of thefts are changing – with a rise in more forceful tactics, and, as in the Louvre case, a focus on high-value items such as precious metals and gemstones.

Both Brand and Ibrahim Bulut, a museum security expert from a Belgian security consulting firm, believe many thefts that followed the Louvre burglary are copycats.

“Every museum in the world is stressing now,” Brand says. “In every museum there have been meetings with the security officer or with the police.”

The Association for Research into Crimes against Art (ARCA) says the recent thefts show “a repeated preference for small, portable, immediately accessible objects and for attacks designed to be completed in minutes”.

Data provided to the BBC by ARCA shows recorded museum thefts in France spiked in 2024, and rose again slightly in 2025.

However, numbers go up and down over time, with more thefts recorded in 2015 than a decade later.

These crimes threaten what many consider invaluable artefacts of historical and cultural value enjoyed by the public – although some people argue they steal “from the rich, who cares?” Brand says.

Others point out the colonial history behind many treasures in European museums, with art historians highlighting the French crown jewels stolen from the Louvre contained emeralds, diamonds, sapphires and pearls which are not native to France.

Museums are vulnerable and easy to burgle, Brand says, compared with well-secured jewellery shops and banks – which these days hold less cash.

Directors historically “never have enough money for security” or prefer to spend it on the next exhibition, and museums are often housed in old buildings that are difficult to protect, he adds.

For example, the Denis Diderot Maison des Lumières (House of Enlightenment) – burgled hours after the Louvre – is housed in two 18th-Century mansions in Langres.

“We therefore have to reconcile modern security requirements with the need to preserve historic buildings and comply with France’s heritage regulations,” local mayor Théo Caviezel explains.

Museums are also open public spaces that have less access control and perpetrators can come in as visitors, says Kumar Sokka, CEO of Acre Security which works with some museums in Europe.

And even if a museum is secured well, thieves could still come in armed, Brand says, adding that it would be impractical to put police in galleries.

Many of these burglaries are over in minutes and the thieves have long gone by the time police show up – the Renoir case happened within five minutes.

Heists used to depend on deception, but burglaries are now becoming increasingly violent, Europol’s report last month, external points out. Offenders are using tools such as sledgehammers, axes, crowbars and, in some instances, explosives, to get inside.

In the Louvre, the thieves used a mechanical lift to gain access, cut through the window with power tools and then threatened guards, who left, before forcing their way inside displays and grabbing the jewels. In the Renoir case, the perpetrators used an electric knife to cut through a fence before sawing through structures holding the paintings’ frames in place.

The increased aggression creates new security concerns.

“An armed incident during opening hours, like the one we experienced, creates a situation in which the immediate priority is to keep our audience and staff safe,” says Lilli Hollein, the director of the Museum of Applied Arts (MAK) in Vienna, which was burgled last month.

What is being stolen is also changing. While paintings are still taken, they’re harder to sell, so about 10 years ago, thieves began shifting to goods that are easier to get rid of, Brand says.

Now precious metals, gemstones, and culturally significant artefacts including Chinese porcelain are increasingly targeted, according to Europol’s report.

“Precious metals can be easily melted down, leaving no trace for law enforcement, and facilitating illicit sales during the fencing process,” it says. “Precious stones in jewellery, on the other hand, can be easily removed and sold further.”

Meanwhile, Chinese porcelain is likely to be easily sold on the art market because of high demand, Europol says.

After a theft, police generally have between four and six days to catch the thieves, according to Brand, who works with investigators by calling informants and receiving tips from the public or even ex-partners of perpetrators.

But while suspects may be arrested, jewels or precious metals might not be found – such as with the Louvre case.

On the other hand, Brand believes the Renoir paintings stolen this week – two of which were dropped by the thieves on their way out – “will probably be recovered” because “no one will want to buy” them and “it is likely, then, that the thieves have no idea what to do with them”.

Christopher A Marinello, the boss of Art Recovery International that recovers stolen art, says only 5-10% of stolen art is ever recovered, making thefts from small museums like this week’s “extra painful”.

Tuesday’s heist is another example of “Europe’s museums under siege”, he adds.

After its theft in October, Maison des Lumières launched a security audit carried out by police officers appointed by France’s cultural ministry, mayor Caviezel says.

Some recommendations are already being implemented, such as enhanced video surveillance, while other structural improvements are in the process of being developed.

MAK in Vienna also increased its security to prevent “copycat offenders and to provide our audience with visible security”, its director says. Entry is through a metal detector, and bags must be put in the cloakroom or in lockers, and there are more security guards.

Experts say the trick is to create physical barriers that will delay thieves so there is time for the police to arrive, or to make any theft take so long that it would deter would-be offenders from attempting it.

“Security is about buying time”, says Bulut. “The objective is not to make the theft theoretically impossible, but to make removal difficult, noisy, detectable and above all, time-consuming, because to be very honest, thefts can always happen, it’s the timing that you’re concerned about.”

Brand says a delay could be building an extra, heavy door anchored into the ground, thickening the glass on display cases or using a fog machine.

Sokka says it’s critical to have integrated systems – so for example if an alarm goes off, you could shut down the facility, or lock down all high net worth paintings.

However, security measures are expensive. Mayor Caviezel, whose small French city hosts two museums and collections, says finding the money is “one of our main challenges”.

“A small city can be entrusted with collections of national importance without having the financial resources of a major Parisian institution.”

Bulut, who sits on the International Committee for Museum Security board, says it’s not all about expensive gadgets. It could also be training guards to spot suspicious people who may be casing a museum and ask them if they need help, which may deter them from returning.

Museums are investing: Sokka says his company has seen an uptick in seismic offerings, that can detect vibration such as drilling in walls, in the past 18 months.

Museum heists are not increasing everywhere in Europe. In Sweden, major museum thefts began to decline around a decade ago and have not changed significantly in recent years, said Peg Magnusson, Sweden’s representative for a Unesco convention to combat illicit trafficking of cultural property. However, other worrying cultural artefact targets have emerged.

The challenge for museums now is increasing security while also staying open to the public.

“A museum cannot be a fortress,” Hollein says. “We want to be open institutions; at the same time, we are facing new challenges and attacks against museums that will require new standards.”

Additional reporting by Madeleine Lake.