The head of the African Union Commission, Chad's Moussa Faki Mahamat, denounced the "violent and degrading treatment of African migrants" on Friday during an attempt to enter the Spanish enclave of Melilla.
He has called for an investigation into the tragedy, which will be examined on Wednesday by the UN Security Council.
"I express my deep emotion and concern at the violent and degrading treatment of African migrants seeking to cross an international border between Morocco and Spain," Moussa Faki tweeted Sunday evening.
"I call for an immediate investigation into this matter and remind all countries of their obligations under international law to treat all migrants with dignity and prioritise their safety and human rights while curbing any excessive use of force," the AU Commission head added.
In a tweet, Kenya's ambassador to the UN Martin Kimani announced that at his country's initiative, supported by Gabon and Ghana - the other two African countries currently non-permanent members of the Security Council - it would hold a closed-door meeting on Friday's violent crackdown on migrants.
According to diplomats, the session was initially planned for Monday but was eventually postponed until Wednesday. It will focus on "the deadly violence faced by African migrants entering" the Spanish enclave of Melilla from Moroccan territory, the Kenyan diplomat said.
"Migrants are migrants: whether they come from Africa or Europe, they do not deserve to be brutalized in this way," said Martin Kimani. Asked about Friday's tragedy during his daily press briefing, UN spokesman Stephane Dujarric said the UN "deplores this tragic event and the loss of life" that resulted from it.
Spain had previously praised Rabat's "collaboration" "in defending (its) borders" on Monday, while many voices are calling for an investigation into the deaths of the migrants. The Moroccan judiciary has decided to prosecute 65 migrants, mostly Sudanese, for their participation in Friday's deadly attempted crossing.
The prosecutor's office of the court of first instance in the northern Moroccan city of Nador, which borders Melilla, has charged 37 migrants with "illegal entry into Morocco", "violence against law enforcement officers", "armed gathering" and "refusal to comply", their lawyer Khalid Ameza told AFP. A second group, consisting of 28 migrants, will also be tried for "participation in a criminal gang to organise and facilitate illegal immigration abroad".
The lawyer said that the majority of the defendants were from Darfur, in western Sudan, which is in the grip of a serious food crisis and where recent violence has left more than 125 people dead and 50,000 displaced. Others are Chadian and Malian, and one is Yemeni.
Some 50 NGOs, including the Moroccan Association for Human Rights (AMDH) and the Spanish Caminando Fronteras, denounced "a tragic symbol of the European Union's policies of externalising its borders". They added: "The death of these young Africans (...) reveals the deadly nature of the security cooperation on migration between Morocco and Spain".
The Spanish Ombudsman, seized by NGOs, has asked for explanations "from the services concerned". At least 23 migrants died and 140 police officers were injured, according to the Moroccan authorities, when some 2,000 migrants attempted to enter the Spanish enclave of Melilla, in Moroccan territory.
The death toll is the highest ever recorded in the numerous attempts by sub-Saharan migrants to enter Melilla and the neighbouring Spanish enclave of Ceuta, the European Union's only land borders with the African continent.