The United Nations peacekeeping chief said an escalation in fighting in Darfur has forced 138,000 people to flee their homes since mid-January and there is no end in sight to the 13-year conflict in western region of Sudan.

Herve Ladsous told the UN Security Council on Wednesday that there is upsurge in fighting in Darfur's Jebel Marra area between Sudanese government forces and rebels loyal to the Sudan Liberation Army's founder Abdul Wahid Mohammed al-Noor.

He added that government has blocked access to the joint UN-African Union peacekeeping force in Darfur known as UNAMID and humanitarian organizations from entering into fighting areas, so the number of casualties is unknown, he said.

The Security Council briefing follows a report from U.N. experts monitoring sanctions against Sudan dated mid-December that has been circulated to council members but not released because of Russian objections to some recommendations.