An elite contingent of Nigerian soldiers has left for Sudan's troubled Darfur region to bolster an African Union peacekeeping force there.

Nigerian military officials say about 50 troops left the Nigerian capital, Abuja, Thursday on a U.S. military transport plane. Nigeria is expected to send at least 350 more troops to Darfur in the next few weeks.

The contingent will bolster a force of 300 African Union soldiers protecting 150 observers already in Darfur to monitor a cease-fire between rebels and Arab militias.

Human rights groups have called on the 53-member African Union to use soldiers to protect civilians from government-backed Arab militias, known as Janjaweed, who have driven them from their homes.

Some information for this story provided by AP and Reuters.