From a few thousand fighters in a handful of countries a decade ago, the number of foreign fighters leaving home to join groups like al Qaeda and the "Islamic State" (IS) has skyrocketed to 25,000 people from over 100 nations according to a United Nations report obtained by the media late Wednesday.

The report made by experts at the behest of the UN Security Council said the number of foreigners joining militant organizations had increased by 71 percent between mid-2014 and March 2015, making the scale of the problem "higher than it has ever been historically."

The experts describe groups like IS and the Al-Nusra Front as forming a "veritable 'international finishing school' for extremists," particularly in Syria and Iraq, where 20,000 of the foreign militants are thought to be living and working.

Afghanistan's own security forces estimated in March that around 6,500 foreign fighters were active in their country. The report also suggested that the problem had spread significantly in Yemen, Libya, and Pakistan, and to a lesser but still significantly in Somalia, several nations in northern Africa, and the Philippines.

The report highlighted the rise in origin countries from a small group in the 1990s to over 100, more than half the nations of the world. It cited the "high number" of militants leaving from Tunisia, Morocco, France, and Russia as well as an increase in fighters from the Finland, the Maldives, and Trinidad and Tobago.

Those who eat together can bomb together

With globalized travel, the panel of experts said, the chance of a person from any country "is growing, particularly with attacks targeting hotels, public spaces and venues." The report also emphasized that the increase in foreigners joining militant organizations is "an urgent global security problem" that must be addressed on several fronts and doesn't have any easy solutions.

"Those who eat together and bond together can bomb together," the experts wrote. "The globalization of al Qaeda and associates, particularly visible with (Islamic State), but also evident with al Qaeda in the Arabian Peninsula (in Yemen), creates a deepening array of transnational social networks."

The panel's report said the most effective policy governments can implement is prevention of radicalization, recruitment, and travel of the would-be fighters. They noted that less than 10 percent of basic information for identifying foreign fighters was being shared, and called for greater intelligence cooperation. The report gave the positive example of the "watch list" in Turkey, a key transit point to Syria and Iraq, which has grown to include 12,500 individuals.

es/sms (AP, Reuters)