( 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 . If true , he says , ` ` We are looking at what amounts to mass murder in the Mediterranean '' He tells of people ' laughing as they rammed the boat , watched it sink . Children are among as many as 500 people feared dead ; 11 survivors have been found .