UNITED NATIONS -- The threat to international peace and security posed by ISIL terrorist fighters is "on the rise again," the UN counter-terrorism chief Vladimir Voronkov told the Security Council on Wednesday.

Despite the competing priorities brought by the COVID-19 pandemic, Voronkov, head of the UN Office of Counter-Terrorism (UNOCT), said that it is "crucial" for member states to remain focused and united in thwarting terrorism.

"While ISIL has not developed a purposeful strategy to exploit the pandemic, its efforts to regroup and to reinvigorate its activities (has) gained further momentum," he said.

Via a videoconference, the UN official flagged that the terrorists, also known in Arabic as Da'esh, have maintained the ability to move and operate, including across porous borders.

At the same time, the pandemic's socio-economic toll and political fallout could further render individuals receptive to radicalization and recruitment.

As the international community continues to grapple with the legacies of the group's so-called "caliphate," the UNOCT chief said that some 10,000 ISIL fighters, mostly in Iraq, are pursuing a protracted insurgency, posing "a major, long-term and global threat."

"They are organized in small cells hiding in desert and rural areas and moving across the border between the two countries, waging attacks," he elaborated.

Voronkov also spoke of the precarious situation of the mostly women and children with links to the fighters, zeroing in on the dire humanitarian and security situation in detention facilities and displacement camps, "especially in al-Hol."

"Nearly two years after the territorial defeat of ISIL, some 27,500 foreign children are still in harm's way in the camps in northeast Syria, including about 8,000 children from some 60 countries other than Iraq," he said, adding that 90 percent are under 12.

Based on humanitarian urgency, moral imperative and legal obligations, the UN official echoed the secretary-general's call to member states to "voluntary repatriate adults and children stranded in Iraq and Syria."

The UNOCT head briefed the Council on ISIL's activities in West Africa, Asia and Southeast Asia, recalling two suicide bombings conducted by women in the Philippines last August.

And he updated on his office's activities, including the launch of a Global Programme on Prosecution, Rehabilitation and Reintegration - in close cooperation with the Counter-Terrorism Committee Executive Directorate (CTED) and the UN Office on Drugs and Crim (UNODC) - to assist Indonesia, Burkina Faso and Lake Chad Basin States, with Mozambique support on standby, if requested.

Noting that 2021 is the 20th anniversary of Resolution 1373, which the Security Council adopted on countering terrorism in the wake of the 9/11 terror attacks in the United States, Voronkov urged member states to recommit themselves under UN auspices to "multilateral action against terrorism."