The threat of an attack by Islamist militants in Europe is "real" and EU countries must all remain mobilised to counter it, France's interior minister Bernard Cazeneuve warned Friday.

His remarks came amid signs that the number of jihadists leaving Europe to fight in Iraq and Syria continued to increase, raising concerns that some will return to their home countries battle hardened and ready to carry out attacks.

"There are risks which are real today and which require a general mobilisation," Cazeneuve said after a meeting of EU interior ministers in Brussels to discuss the threat posed by foreign fighters.

A European official presented the threat in even starker terms, telling AFP on condition of anonymity that "an attack on European territory is very likely."

Another European source added: "The motives to join the jihad will continue as long as the conflict in Syria and Iraq lasts."

Cazeneuve said that in France the number of people involved in the jihadist network has jumped by 89 percent since the beginning of the year.

Some 1,150 French citizens are part of the network, including 300 to 350 on the ground, more than 50 who have died and some 200 who have returned to France. The remainder of the network involves recruiters and supporters.

The Europe Union's counter-terrorism chief Gilles de Kerchove said the number of Europeans joining Islamist fighters in Syria and Iraq is around 3,000.

De Kerchove said security officials fear not so much a large-scale, coordinated attack like that of September 11, 2001 in the United States, but something more like the one at the Jewish museum in Brussels that killed four people in May.

"Each country works on foiling attacks on its territory," Cazeneuve said.

"We do it in France. There are operations, arrests ...every day to avoid it happening," he said.

"I'm used to saying that zero precautions amount to 100 percent risk, but 100 percent precautions do not reduce the risk to zero."

The French parliament last month adopted a counter-terrorism law which bans people from leaving the country if they are suspected of trying to wage jihad in Syria.

Cazeneuve, like de Kerchove, supports other measures to fight the problem of foreign fighters.

Though long rejected by the European Parliament, one idea is to agree a European Passenger Name Record (PNR) system, enabling countries to swap data on all airline passengers that notably could help trace would-be militants.

"We need a compromise. We must better incorporate the concerns of parliament, which are legitimate concerning the protection of personal data," Cazeneuve said.

"Once guarantees are given on protecting data, the European parliament must in return accept the idea that fighting terrorism without the European PNR is a lot more difficult than if we have all the tools to do it," he said.

Britons jailed for Syria-related terror offences
London (AFP) Dec 05, 2014 - Two British men were sentenced to prison for terror offences Friday, as security forces crack down on what they say is a mounting threat from jihadists radicalised by the Syria conflict.

Childhood friends Mohammed Ahmed and Yusuf Sarwar, both aged 22 from Birmingham in central England, were jailed for 12 years and eight months each.

In a separate case, Mashudur Choudhury, a father of two in his early 30s from Portsmouth on the southern English coast, was sentenced to four years jail for engaging in preparation of terrorist acts.

Ahmed and Sarwar, who pleaded guilty, were jailed for the same offence after travelling to Syria, where they are believed to have spent eight months with Al-Qaeda's Syrian affiliate the Al-Nusra Front.

They went to Syria in May last year after contacting Islamic extremists, and were arrested on their return to Britain in January, a court heard.

"They willingly, enthusiastically and with a great deal of purpose, persistence and determination embarked on a course intended to commit acts of terrorism," judge Michael Topolski said.

"Both of these defendants are fundamentalists who are interested in and deeply committed to violent extremism," he added.

However, former Guantanamo Bay detainee Moazzam Begg said the pair had been branded "terrorists" despite having "no intention of harming anyone".

"I spent several months in prison with these two men and I do not consider them to be a threat to the British public in any way, just in the same way the police that arrested them said they posed no threat whatsoever," he said.

"They never joined Islamic State nor expressed intention to do so; rather, they returned back home.

"This case must be taken to appeal."

Meanwhile Choudhury, who in May became the first person to be convicted in Britain of terror offences related to the Syria conflict, was found guilty of engaging in preparation of terrorist acts.

Choudhury was part of a group of up to six young men who travelled from Portsmouth to Syria in October last year, with the intention of attending a terrorism training camp, his trial heard.

Four of the group have already been killed in fighting, according to reports.

British security forces have stepped up surveillance and arrests of terrorism suspects in recent months, and lawmakers are set to toughen anti-terrorism laws in a bid to stem the flow of Britons joining Islamic State (IS) jihadists fighting in Syria and Iraq.

An estimated 500 Britons have travelled abroad to become jihadists and officials fear the return of battle-hardened and radicalised fighters.

The self-proclaimed Islamic State group aims to create a "caliphate" straddling Syria and Iraq, and has proved adept at using social media, gruesome online videos and glossy literature to attract thousands of volunteers.