According to media reports, the migrants are feared drowned after a boat they were traveling in capsized off the coast of Libya.
This would be the worst such tragedy in the Mediterranean this year, the UN said in a statement.
In a tweet, Guterres said he was “horrified” by the news, and called for “safe, legal routes for migrants and refugees”.
His comments were echoed by heads of several UN agencies who have called for a return to sea rescues in the Mediterranean.
They include Head of the UN Refugee Agency (UNHCR), Filippo Grandi, and his Children’s Fund counterpart, Henrietta Fore.
Brandi and Fore had earlier called for an end to the “arbitrary detention of refugees and migrants in Libya”.
In a social media report on Thursday, the Libya office of the International Organisation for Migrants (IOM) said some 145 survivors of the shipwreck, mainly Eritreans and Sudanese, were returned to the Libyan shore.
The survivors reported that some 250 were on the boat before it capsized, after engine failure, the UN stamens said.
(By Harrison Arubu – NAN)