AMSTERDAM (AP) — The European Union on Monday launched a new law enforcement center to coordinate the fight against violent extremism, saying Europe faces the most significant terrorist threat in over 10 years.

"There is every reason to expect that IS (the Islamic State organization), IS-inspired terrorists or another religiously inspired terrorist group will undertake a terrorist attack somewhere in Europe again, but particularly in France, intended to cause mass casualties among the civilian population," Europol, the EU-wide agency for law enforcement cooperation, said in a report. "This is in addition to the threat of lone-actor attacks, which has not diminished."

The report coincided with the official opening of the European Counter Terrorism Center. Europol director Rob Wainwright said his organization's new unit in The Hague, Netherlands will be staffed by 40-50 experts in counterterrorism and deal in intelligence-sharing, tracking foreign fighters and sources of illegal financing and firearms, and assisting EU countries in counterterrorism investigations.

Wainwright said over 5,000 EU nationals have been radicalized by fighting with Muslim extremists in Iraq and Syria, and that many have returned home.

"The current threat demands a strong and ambitious response from the EU," said Europol's chief.