"I express my deep shock and concern at the violent and degrading treatment of African migrants attempting to cross an international border from Morocco into Spain," AU Commission chief Moussa Faki Mahamat said in a statement on Twitter late Sunday.
"I call for an immediate investigation into the matter and remind all countries of their obligations under international law to treat all migrants with dignity and to prioritize their safety and human rights, while refraining from the use of excessive force," his statement added.
About 2,000 migrants stormed the heavily fortified border between the Moroccan region of Nador and the Spanish enclave of Melilla on Friday.
At least 23 migrants died and 140 police officers were wounded in the ensuing violence, according to Moroccan authorities. It was the heaviest toll in years from such attempts to cross that fortified frontier.
enya's ambassador to the United Nations, Martin Kimani, said a UN Security Council meeting would be held behind closed doors on Monday to discuss the violence African migrants face in Melilla.
Kenya, Gabon and Ghana -- the African non-permanent members of the Security Council -- called for the meeting, he said.
"Migrants are Migrants: whether from Africa or Europe, they do not deserve to be brutalised in this way," Kimani wrote on Twitter.
Speaking at a regular press briefing, UN chief Antonio Guterres's spokesman Stephane Dujarric said: "We very much deplore this tragic incident and the loss of life."