U.N. Secretary-General Ban Ki-moon warned Monday that DAESH could set up new cells across Libya and north Africa as they are driven from their stronghold of Sirte. Ban outlined the threat from foreign terrorist fighters (FTF) in Libya in a confidential report to the Security Council, obtained by Agence France-Presse (AFP).

"The recent pressure against DAESH in Libya could lead its members, including FTFs, to relocate and regroup in smaller and geographically dispersed cells throughout Libya and in neighboring countries," Ban said in the report.

The defeat of DAESH extremists in Sirte "appears to be a distinct possibility," leading many to flee south as well as west, to Tunisia. "The future impact of scattered DAESH combatants on southern local armed groups may become an issue of concern," he said.

Libyan forces allied with the U.N.-backed government in Tripoli have been battling to take Sirte from DAESH extremists for the past two months. The coastal city is considered one of DAESH's most important rear bases outside of Syria and Iraq.

There are between 2,000 and 5,000 DAESH fighters from Libya, Tunisia, Algeria, Egypt, Mali, Morocco and Mauritania deployed in Sirte, Tripoli and Derna, according to the report. Dozens of foreign fighters from Tunisia have returned home from Libya "with the intent to conduct attacks," it added.

Mokhtar Belmokhtar, leader of the al-Mourabitoun group active in the Sahel, is able to travel throughout Libya with relative ease while the head of Ansar Dine in northern Mali, Iyad Ag Ghaly, maintains a foothold in southern Libya, the report said.