UNITED NATIONS, Feb. 5 -- UN Secretary-General Ban Ki-moonon Friday said that 34 militant groups worldwide had reportedly pledged allegiance to the Islamic State (IS) extremist group as of mid-December.

Militant groups from countries like the Philippines, Uzbekistan, Pakistan, Libya and Nigeria had pledged their allegiance, so IS poses "an unprecedented threat," Ban said in a report on the challenges IS poses to international peace and security.

The emergence of IS has been facilitated by the protracted conflicts in Iraqand Syriaand the resulting political and security instability, he said.

"In less than two years, ISIL (another acronym for IS) has captured large swathes of territory in both Iraq and the Syrian Arab Republic, which it administers through a sophisticated, quasi-bureaucratic revenue-generating structure that is sufficiently flexible and diversified to compensate for declines in income from single revenue streams," he said.

The recent expansion of IS influence across west and north Africa, the Middle East and south and southeast Asia demonstrates the speed and scale at which the gravity of the threat has evolved in just 18 months, he added.

In 2016 and beyond, UN member states should prepare for a further increase in the number of foreign terrorist fighters travelling to other countries on the instructions of IS, said Ban.

Despite efforts by the international community to counter IS through military, financial and border-security measures, the group continues to maintain its presence in Iraq and Syria. It is also expanding its operations to other regions.