Europe's estimated 60,000 radicalised Islamic militants, of which around 20,000 are found in France alone, will remain a threat for years to come, according to an expert.

"That is no doubt the main thing which is going to be of a direct concern for years going forward," Jean-Charles Brisard of the Paris-based Centre for the Analysis of Terrorism, told MEPs on Monday (9 April).

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Brisard said that while the Islamic State (IS) group may have lost territory in Iraq and Syria, its operational capacity to carry out attacks had not diminished and "remains very much a force to be reckoned with."

He noted that the group has since morphed into a global terrorist network, making the threat more elusive and difficult to tackle.

"Reducing the territory of the Islamic State and thinking that this would cause the threat to simply disappear was misguided," he said.

The group is now implanted in places like Afghanistan, Libya, Philippines, and Yemen.

Few European nationals, who fought alongside the Islamic State, are returning home as people continue to travel to the areas to join terrorist ranks, Brisard said.

Many have either been killed in action, captured, or moved onto other theatres of battle. Some of those returned will have combat experience and training and may carry out attacks.

Since 2012, around 258 foreign fighters have returned to France, he noted, of which most remain detained while awaiting a trial.

He noted that some 50 percent of the perpetrators in Europe were of the nationality of the target country, while around 10 percent of the individuals involved had spent time in other countries, in many cases unbeknownst to the authorities.

"Overall, the Union ... had a terrorist attack of some kind every six days [in 2017]," he said. France had the most, followed by the UK and Germany.

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Operational modes are also now more improvised and weapons becoming increasingly rudimentary.

Vehicles, knives, and home made bombs are among the more common methods of waging terror. Such methods come at little to no expense, posing broader questions on efforts to track and crack down on terror financing.

"Bloody attacks can cost little or nothing in certain cases," Raphael Malagnini, a Belgian federal magistrate working for the prosecutor's office, said at the same EU event on Monday.

Although the Paris attack in November 2015 is estimated to have cost €82,000, he said most European terrorist cells are largely self-financed with small budgets.

Last June, one individual had attempted to blow himself up in the Brussels central train station. The bomb malfunctioned but the following inquiry suggested the perpetrator had spent only a few hundred euros to build the device.

The vehicle used at a Christmas market attack in Berlin in 2016 had been stolen, while the truck used to kill 86 people in Nice in July 2016 had been rented.

Malagnini noted that terror groups have since 2001 spent between $200,000 and $500,000 to carry out attacks compared to the "thousand billion dollars" spent by US authorities to counter them.

A lot of the terrorist money goes on spreading propaganda to secure new recruits, he said.

He also noted that groups like Islamic State have little use of traditional banking methods but instead confiscate assets and exploit natural resources in areas they control.

"The measures when it comes to terrorist financing and combatting terrorist financing present a fairly limited interest in terms of the current threat and also in terms of prevention of those threats," he said.

But Pierre Moscovici, the EU tax and finance commissioner, told MEPs efforts at the EU level are underway to make it more difficult for terror and organised groups to secure funding.

He noted that the EU is tightening rules on cultural goods to make it more difficult for archaeological artefacts looted in place like Libya to find a client base in Europe.

"I count on both co-legislators to adopt this text by the end of this legislative period, I would really urge for this process to be speeded up," he told MEPs.

Another proposal aims to make it more difficult to send more than €10,000 in cash by mail. It also seeks to crack down prepaid cards and on undeclared gold.