Radical youths from Europe and the Arab world are being trained in Iraq, Europe's anti-terror chief said Tuesday, warning that such clandestine camps could multiply in unstable or failed states anywhere in the world.

"There are some who have gone to Iraq, as indeed there have been youngsters from outside Europe, from Arab countries, who have gone there to receive military training," EU counterterrorism coordinator Gijs de Vries (search) said in an interview with The Associated Press.

De Vries refused to elaborate on the specifics, such as the numbers or countries of origin of those training in Iraq, saying the information was classified.

But he warned that action had to be taken to stop instability breeding terror.

"This is incidentally not just the case in Iraq," he said. "Instability elsewhere in the world, in Africa for example, always makes it more difficult for the law to be upheld, for democracy to function, and therefore makes it easier for terrorists to hide and train."

In other comments, De Vries said Europe should not become complacent in spite of a lull in attacks since the March 11 train bombings in Madrid and the foiling of plots in several countries.

"Overall, we can say that the threat of terrorism in Europe remains high," De Vries said. "We should take it very seriously indeed."

Spanish and British authorities say they have averted major terror attacks in recent months.

In October, 30 people were detained on suspicion of planning to drive an explosives-packed truck into Madrid's National Court. British police said last week they had prevented an attack in London on the scale of the Madrid bombings.

"There have been other instances," De Vries said, but refused to give details.