The war raging in Syria has "provided the perfect breeding ground for extremist and terrorists to take root in the society," UN Secretary-General Ban Ki-moon told reporters in Geneva.
"Now (the Islamic State group) and all the extremists are spreading like a cancer around the world," he warned in remarks on the sidelines of a high-level conference on preventing violent extremism.
In an earlier address to some of the 700 delegates -- among them around 30 ministers and deputy ministers -- Ban urged a radical rethink of ways to counter the threat from Isis and other groups.
"Evidence shows that security and military responses alone cannot defeat this scourge," he said, stressing that heavy-handed responses have sometimes "proven to be counter-productive" and can "end up further fuelling violent extremism".
In January, Ban launched a global action plan, asking countries to come up with national plans to address the problem.
Ban's plan encompasses 79 recommendations, from boosting education to promoting human rights to counter the recruitment drives of groups like IS and Boko Haram which prey on disaffected youth.
It also calls for countries to try to appeal to fighters who have joined groups like Isis to return home by offering education and job opportunities, and urges governments to engage with social media to find ways to challenge the jihadists' messages.
Belgian Foreign Minister Didier Reynders, whose country last month was rocked by terror attacks that killed 32 people, was among the many ministers who voiced support for Ban's plan.
"We must remain vigilant to ensure that our fight against terrorism respects freedom of expression, the freedom of citizens," he told delegates.
"Respecting human right is not only an efficient way to fight terrorism, but it is also a way to not give in to the terrorists," he said.
Swiss Foreign Minister Didier Burkhalter, whose country co-hosted the conference, agreed.
"Preventing violent extremism means stepping up efforts to promote the rule of law, human rights and, in armed conflicts, international humanitarian law," he told the conference.
Countries also need to "offer young people opportunities and render them unreceptive to the temptations of terrorism," through education and job opportunities, he said.
Ban said Friday he aimed to create a high-level action group to review and help implement his plan to prevent violent extremism.