UNITED NATIONS, Feb. 10 (Xinhua) -- The Islamic State (IS) terrorist group remains a serious global security threat and multilateral cooperation is essential to combatting terrorism effectively, the UN's top counter-terrorism official said on Monday.

"Terrorism remains a significant and evolving threat to global peace and security, one that no state can confront in isolation," Vladimir Voronkov, under-secretary-general for the Office of Counter-Terrorism, said during his briefing to the UN Security Council.

Voronkov underscored that sustained multilateral cooperation remains essential to countering terrorism effectively.

The volatile situation in Syria "is of great concern, especially as there is a risk that stockpiles of advanced weapons could fall into the hands of terrorists," he said, adding that the risk is particularly high in Badia region, which serves as the hub for the IS external operational planning.

In Afghanistan, ISIL-K, one of the most dangerous branches of the Islamic State, continued to pose a significant threat, Voronkov said. "In addition to attacks in Afghanistan, ISIL-K supporters plotted attacks in Europe and were actively seeking to recruit individuals from Central Asian States."

He warned against Afghanistan becoming again a hot bed of terrorist activities.

Meanwhile, in sub-Saharan Africa, the Islamic State and its affiliates continue to increase their operations and expand territorial control.

"The situation is deeply concerning in West Africa and the Sahel," where the IS affiliates and other terrorist groups intensified attacks, including against schools in Burkina Faso, Mali and Niger, Voronkov told the council.

"As sub-Saharan Africa has become the epicentre of global terrorism, we have prioritized capacity-building support to the continent," he noted.

The UN counter-terrorism chief called for collective, multilateral action to counter the evolving and persistent threat posed by the terrorism, stressing "the terrorist group's ability to exploit instability highlights the need for sustained international collaboration."

Voronkov urged states to prioritize comprehensive, long-term responses that address the conditions conducive to terrorism while strengthening the rule of law.