Geneva: The deaths of up to 500 migrants and refugees in an intentional boat-ramming in the Mediterranean Sea last week could be an act of mass murder, the UN rights chief said on Friday, calling for nations to properly investigate the incident.

Up to 500 Syrians, Palestinians, Egyptians and Sudanese migrant workers and refugees were aboard the boat that left from the Egyptian port of Damietta and are feared dead at the hands of human traffickers who rammed and sank the boat off the Malta coast.

“The callous act of deliberately ramming a boat full of hundreds of defenceless people is a crime that must not go unpunished,” UN High Commissioner for Human Rights Zeid Raad Al Hussain Zaid said in a statement. “If the survivors’ accounts are indeed true — and they appear all too credible — we are looking at what amounts to mass murder in the Mediterranean.”

According to survivors interviewed by staff from the International Organisation for Migration, there may have been 100 children under the age of 10 aboard the boat, among several hundred people crammed into a lower boat deck, while a couple hundred more were on a top deck constantly exposed to the sun.

The IOM said the smugglers charged up to $4,000 (Dh14,691) apiece to board the overcrowded, creaky boat, and then forced them to switch boats in mid-sea numerous times.

“All countries would throw the full weight of their police forces and justice systems behind an investigation if the victims were their own citizens and were killed by criminal gangs on their own soil,” Zaid said. “The reaction should not be any less rigorous just because the victims are foreigners and the crime took place on the high seas.”

All of the witnesses told IOM staff that the smugglers were Egyptian or Palestinian. Zaid urged the Greek, Maltese and Italian authorities to share information on the identity of the smugglers with Egyptian authorities, who should launch a thorough investigation.