The United Nations Secretary-General Antonio Guterres is “gravely alarmed” by reports of a full-scale assault on North Darfur’s city of el-Fasher in Sudan, says a UN spokesperson.

Guterres on Saturday called on the leader of the paramilitary Rapid Support Forces (RSF) to immediately halt the attack, warning that any further escalation threatens to spread the conflict along intercommunal lines throughout the country’s Darfur region, the spokesperson said in a statement.

Darfur has seen some of the war’s worst atrocities, and the RSF has besieged el-Fasher since May – but fighting has escalated in the past week.