The United Nations human rights chief has warned that a humanitarian catastrophe is developing in Sudan's el-Obeid - urging world leaders to act now to prevent atrocities.

The emergency session follows warnings that 500,000 civilians around el-Obeid are at risk of large-scale atrocities.

As RSF troops besiege el-Obeid, 500,000 civilians face mass atrocities amid drone strikes and a stalled peace process.