The United Nations is warning that a large number of Arab militia are assembling in Sudan's war-torn Darfur region for an unknown reason.
The U.N. Mission to Sudan says the fighters are suspected to be Janjaweed, the militia blamed for numerous cases of rape, arson and killing during the four-year Darfur conflict.
It says the militias are assembling north of El Geneina, the capital of West Darfur state, and said the reason for the gathering is not clear. The mission did not say exactly how many militiamen are gathering but described the number as "significant."
The U.N. and other international organizations have accused Sudan's government of arming the Janjaweed to aid its campaign against Darfur rebels. Sudan denies the accusations.
On Tuesday, Sudan's President Omar al-Bashir traveled to Libya for talks on ending the Darfur crisis.
Sudan's official news agency says the president will meet with Darfur rebels who refused to join a peace deal the government signed with the largest rebel group last year.
The fighting in Darfur has killed at least 200,000 people and driven more than two million others from their homes.
President Bashir has resisted allowing U.N. peacekeepers into Darfur. The U.N. has proposed sending up to 20,000 troops to strengthen an African Union mission that has not been able to control the violence.