The United Nations said Monday that Sudanese security forces' detention of civilian leaders including premier Abdalla Hamdok was "unacceptable." 

"I am deeply concerned about reports of an ongoing coup and attempts to undermine Sudan's political transition. The reported detentions of the prime minister, government officials, and politicians are unacceptable," said Volker Perthes, UN special representative to Sudan.  

"I call on the security forces to immediately release those who have been unlawfully detained or placed under house arrest," he said in a statement on Twitter.