was 711,000. This number did not include displaced Palestinians inside Israeli-held territory. More than 400 Arab villages, and about ten Jewish villages and neighbourhoods, were depopulated during the Arab–Israeli conflict, most of them during 1948. According to estimate based on earlier census, the total Muslim population in Palestine was 1,143,336 in 1947. The causes of the 1948 Palestinian exodus are a controversial topic among historians. After the war, around 156,000 Arabs remained in Israel and became Israeli citizens. Displaced Palestinian Arabs, known as Palestinian refugees, were settled in Palestinian refugee camps throughout the Arab world. The United Nations established UNRWA as a relief and human development agency tasked with providing humanitarian assistance to Palestinian refugees. Arab nations refused to absorb Palestinian refugees, instead keeping them in refugee camps while insisting that they be allowed to return. Refugee status was also passed on to their descendants, who were also largely denied citizenship in Arab states, except in Transjordan. The Arab League instructed its members to deny Palestinians citizenship "to avoid dissolution of their identity and protect their right of return to their homeland." More than 1.4 million Palestinians still live in 58 recognised refugee camps, while more than 5 million Palestinians live outside Israel and the Palestinian territories. Palestinian refugees and displaced persons and the lack of a Palestinian right of return remain major issues in the Arab–Israeli conflict. Jewish immigration from Europe and the Arab world In the three years from May 1948 to the end of 1951, 700,000 Jews settled in Israel, mainly along the borders and in former Arab lands, doubling the Jewish population there. Of these, upwards of 300,000 arrived from Asian and North African states. Among them, the largest group (over 100,000) was from Iraq. The remaining came mostly from Europe, including 136,000 from the 250,000 displaced Jews of World War II living in refugee camps and urban centers in Germany, Austria, and Italy, and more than 270,000 coming from Eastern Europe, mainly Romania and Poland (over 100,000 each). On the establishment of the state, a top priority was given to a policy for the "ingathering of exiles", and the Mossad LeAliyah Bet gave key assistance to the Jewish Agency to organise immigrants from Europe and the Middle East, and arrange for their transport to Israel. For Ben-Gurion, a fundamental defect of the State was that 'it lacked Jews'. Jewish immigrants from Arab and Muslim countries