European crime agency Eurojust recorded a 16 per cent increase in terrorism cases over the past year.
In its latest report, the agency said it had dealt with 94 new requests for help in terrorism-related cases from EU member states.
It organised 24 meetings and co-ordinated 222 ongoing cases related to counterterrorism last year.
In one case, its work with security services in Belgium and Hungary resulted in the arrest of an ISIS extremist who was charged with several murders.
Cases concern ongoing investigations and prosecutions regarding terrorist attacks that had either been committed or were planned. The agency also provided assistance to authorities in investigating people supporting terrorist groups, people producing terrorist propaganda and the instigation of others to commit terrorist acts, leading in one case to the arrest in Spain of an extremist suspected of being one of the "core disseminators" of ISIS terrorist propaganda online.
The agency has worked on almost 8,000 crime cases and has frozen £1.7 billion in criminal assets.
Some of the cases involved the targeting of foreign terrorist fighters travelling to a conflict zone to join the ranks of a terrorist group or to undergo terrorist training.
Others focused on terrorist networks and cells involved in the recruitment, financing and facilitation of the travel or return of fighters.
In some counterterrorism investigations, terrorist activities were committed in combination with other offences, such as human trafficking, migrant smuggling and drugs and arms trade.
"These crimes were often connected to money laundering or tax offences, with possible links to the financing of terrorism, and with computer crime and the forgery of official documents," the report said.
"International judicial co-operation was also successfully used to support victims of terrorist attacks and to safeguard and guarantee their rights."
In 2019, Eurojust launched the European Judicial Counter-Terrorism Register, which aims to provide support in identifying potential links between judicial proceedings and build stronger judicial responses to terrorism.