( CNN ) -- People smugglers accused of causing the deaths of hundreds of migrants when they deliberately rammed and sank their boat in the Mediterranean must be found and punished , the U.N. human rights chief said Friday . Up to 500 people on board are thought to have died after the boat went down last week . U.N. High Commissioner for Human Rights Zeid Ra'ad Al Hussein called on Egypt and other North African and European states to track down those responsible for this `` atrocious incident '' and hold them accountable . `` All the countries in the Mediterranean must make a concerted effort to clamp down on the smugglers who are exploiting one of the most vulnerable groups on the planet and endangering their lives , virtually on a daily basis , purely for financial gain , '' Zeid said . `` The callous act of deliberately ramming a boat full of hundreds of defenseless people is a crime that must not go unpunished . `` 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 . '' Zeid also called for nations to tackle the root causes that led people to undertake such dangerous journeys in a bid to reach European shores . 'They were laughing ' Eleven survivors of the sinking , rescued by authorities in Italy , Malta and Greece , told interviewers from the International Organization for Migration earlier this week that the people smugglers were Palestinian or Egyptian . Those on the boat included Syrians , Palestinians -- many of them from Gaza -- Egyptians and Sudanese , as well as Palestinians , the witnesses said . Two Palestinian survivors explained that they 'd paid $ 2,000 -- money they 'd gotten after receiving grants to rebuild their homes -- at what they called a `` travel '' office in Gaza for their voyage to Italy , according to the IOM . They had packed into a boat in Egypt 's port of Damietta and left on September 6 , they said . They estimated at least 400 men and women , in addition to as many as 100 children , were on board . Five days later , the smugglers allegedly rammed their boat far out to sea between Malta and Greece , causing it to sink , after the migrants refused to move onto a smaller boat they judged to be unseaworthy . They 'd already been forced to transfer vessel several times , the survivors said . `` After they hit our boat they waited to be sure that it had sunk completely before leaving . They were laughing , '' one survivor told the IOM . As many as 300 people were reportedly crammed into a lower deck of the boat , many of them children , while another 200 were on the sun-baked top deck , the IOM said . A week later , only 11 survivors have been found . Zeid urged the Greek , Maltese and Italian authorities to share information on the identity of the smugglers with the Egyptian authorities , who he said should also launch a thorough investigation . `` You can not transport large quantities of foreigners in buses into a major port and cram them on board a ship without the port authorities and other witnesses being aware of what is going on , '' Zeid said . 'This summer 's recipe for death ' According to the IOM , the latest reported sinking would take the death toll off Europe 's shores this year to nearly 3,000 . In 2013 , the organization 's Missing Migrants Project estimated the total for the year to be 700 deaths . In a news release Friday , the group said the reported 500 deaths were `` merely the latest chapter in a horrible story unfolding on Europe 's doorstep . `` Criminality , on top of desperation , has been this summer 's recipe for death â€ ” even murder , according to eyewitness accounts . '' The IOM called for an end to a culture of impunity , fed by poverty and lawlessness , that has allowed criminal gangs to prosper , particularly in Libya . And it urged European nations to reform immigration laws to allow refugees safe , legal migration to Europe . CNN 's Radina Gigova contributed to this report .
U.N. human rights chief urges probe into alleged deliberate sinking of a packed migrant boat . The incident occurred in the Mediterranean Sea on Saturday when migrants tried to cross from Turkey to Greece by boat. Survivor tells of people smugglers laughing as they rammed the boat , watched it sink . Children are among as many as 500 people feared dead ; 11 survivors have been found .