UNITED NATIONS -- The threat posed by Islamic State extremists remains high and has increased in and around conflict zones, and the group’s expansion is “particularly worrying” in Africa’s center, south and Sahel regions, the U.N. counter-terrorism chief said Thursday.

Undersecretary-General Vladimir Voronkov told the U.N. Security Council that the group, also known by its Arabic acronym Daesh, continues to use the Internet, social media, video games and gaming platforms “to extend the reach of its propaganda to radicalize and recruit new supporters.”

“Daesh’s use of new and emerging technologies also remains a key concern,” he said, pointing to its continuing use of drones for surveillance and reconnaissance as well as “virtual assets” to raise money.

Voronkov said the high level of threat posed by the Islamic State and its affiliates, including their sustained expansion in parts of Africa, underscores the need for multifaceted approaches to respond – not just focused on security but on preventive measures including preventing conflicts.

The Islamic State declared a self-styled caliphate in a large swath of territory in Syria and Iraq that it seized in 2014. The extremist group was formally declared defeated in Iraq in 2017 following a three-year bloody battle that left tens of thousands dead and cities in ruins, but its sleeper cells remain in both countries.

Some 65,600 suspected Islamic State members and their families — both Syrians and foreign citizens — are still held in camps and prisons in northeastern Syria run by U.S.-allied Kurdish groups, according to a Human Rights Watch report released in December.

Voronkov said the pace of repatriations remains too slow “and children continue to bear the brunt of this catastrophe.” At the same time, he said, “foreign terrorist fighters” who joined the extremist group are not restricted to Iraq and Syria and “move between different theaters of conflict.”

Voronkov, who heads the U.N. Office of Counter-Terrorism, said “foreign terrorist fighters with battlefield experience relocating to their homes or to third countries further compounds the threat” from Daesh.

Weixiong Chen, acting head of the Security Council Counter-Terrorism Committee’s executive directorate, told members that the failure to repatriate foreign nationals from the camps provides Daesh “with ongoing opportunities to recruit from camps and prisons and facilitate radicalization to violence and the spread of terrorism.”

He said the threat from Daesh “presents a complex, evolving and enduring threat in both conflict and non-conflict zones.”

Chen pointed to Daesh’s continued exploitation of “local fragilities and intercommunal tensions” particularly in Iraq, Syria and parts of Africa and the expansion of its affiliates notably in parts of central, southern and western Africa.

He also cited Daesh’s revenue generation and fundraising through a wide range of ways “including extortion, looting, smuggling, taxation, soliciting donations and kidnapping for ransom” as well as its use of social media and gaming platforms. The Islamic State's dominant means of moving money continues to be unregistered informal cash transfer networks and mobile money services, he said.

Daesh’s access to conventional and improvised weapons, “including components of unmanned aircraft systems and information and communications technologies continue to contribute to the terrorist menace,” Chen said, pointing to its use of improvised, stolen or illegally trafficked weapons to launch lethal attacks against a range of targets.