By John Revill

ZURICH (Reuters) -A spate of school killings in Western Europe has raised pressure on authorities to tackle a problem long seen as a largely U.S. phenomenon, increasing momentum for tougher gun and security laws and more policing of social media.

While mass shootings remain far more common in the United States, four of the worst school shootings in Western Europe this century have occurred since 2023 and two - a massacre of 11 people in Austria and another in Sweden- were this year.

This week's killings in the Austrian city of Graz sparked calls for tighter gun laws by political leaders, mirroring the response of the Swedish government after the 11 deaths at the Campus Risbergska school in Orebro in February.

"Mass shootings, of which school shootings are a part, were overwhelmingly a U.S. problem in the past, but the balance is shifting," said Adam Lankford, a criminologist at the University of Alabama. "The number in Europe and elsewhere is increasing."

Part of the rise stems from copycat attacks in Europe often inspired by notorious U.S. rampages such as the 1999 Columbine High School massacre, according to shooters' own comments or their internet search histories, Lankford said.

"It's like an export from America. These attackers see other people do it and it has a snowball effect."

According to research by Lankford and Jason Silva, shootings carried out by people eager for notoriety were twice as numerous in the United States as in the rest of the world between 2005 and 2010. By 2017-2022, the rest of the world had caught up.

Their data also shows that Europe accounts for a bigger share of mass shootings than it used to.

It should be easier for European politicians to act against mass shootings than the United States, due to the central role of guns in American culture and identity, Lankford said.

The European Union has left gun laws and regulation of social media up to member states. Recent killings have seen a drive by several countries to apply tougher rules.

In Sweden, the government agreed to tighten the vetting process for people applying for gun licences and to clamp down on some semi-automatic weapons following the Orebro killings.

Incidents of violence and threatening behaviour in junior high and high schools rose over 150% between 2003 and 2023, according to a report by Sweden's Work Environment Authority.

In Finland, where a 12-year-old shot dead a fellow pupil and badly wounded two others in 2024, schools practice barricading doors and hiding from shooters. The government has also proposed stricter punishments for carrying guns in public.

Following a deadly December knife attack at a Zagreb primary school, Croatia's government tightened access to schools and mandated they must have security guards.

Germany has gradually imposed tighter controls on gun ownership since school massacres in 2002 and 2009, and last year introduced a ban on switchblades and on carrying knives at public events following a series of knife attacks.

RESISTANCE

Tightening gun ownership was the only way politicians could show they were taking the issue seriously, said Dirk Baier, a criminologist at the Zurich University of Applied Sciences.

"There will certainly be resistance to this, from hunters, sport shooters, or other lobby groups," he said. "However, I think the arguments for tightening the laws will outweigh the arguments against."

Gun laws have also been a hot political topic in the Czech Republic since a student shot dead 14 people at the Charles University in Prague in December 2023.

The country made it obligatory for gun sellers to report suspicious purchases and requires doctors to check whether people diagnosed with psychological problems hold gun permits.

Britain is holding a public inquiry into an attack in Southport where three young girls were stabbed to death last year. UK drama "Adolescence", a story about a schoolboy accused of murder, explores concerns about toxic online culture.

Meanwhile in France, President Emmanuel Macron this month pressed for EU regulation to ban social media for children under 15 following a fatal school stabbing.

What motivated the Austrian school gunman is still under investigation. Police said he was socially withdrawn and passionate about online shooting games.

Most such shootings are carried out by young men, and criminologist Lankford said there was a global phenomenon of perpetrators seeking notoriety that eluded them in real life, driven in part by social media.

"Even if the shooters expect to die, some are excited about leaving behind a legacy."

Austria has relatively liberal gun laws, and President Alexander Van der Bellen said after the attack the legislation deserved closer scrutiny.

Broad support in Austria for tightening gun ownership laws looked probable, although a general ban on private weapons seems unlikely, said political scientist Peter Filzmaier.

(Reporting by John Revill, Alexandra Schwarz-Goerlich, Madeline Chambers, Richard Lough, Simon Johnson, Jan Lopatka , Daria Sito-Sucic, Essi Lehto, and Michael HoldenEditing by Dave Graham)