A new U.N. report says fighters pledging allegiance to the Islamic State group are consolidating their hold on parts of central Libya and gaining ground.

Monday's report by the U.N. mission to the chaotic North African country singles out Sirte, Harawa and Nofliya as areas where Islamic State-affiliated groups have taken new territory in recent months.

Libya remains split between two rival governments who are being urged by the international community to approve a proposed peace agreement. Meanwhile, the U.N. and others have warned that armed groups are exploiting the chaos.

The U.N.'s new Libya envoy, Martin Kobler, takes his post Tuesday.

The new report calls the country's situation "highly volatile" and says all parties in the conflict appear to be committing abuses "that may amount to war crimes."