RAMALLAH, Palestinian Territories: There are some 11 million Palestinians scattered around the world, including more than five million refugees living throughout the Middle East.
Their plight has made headlines in Syria, where the UN agency for Palestinian refugee UNRWA says as many as 100,000 Palestinians may have fled the Yarmuk refugee camp in Damascus in recent days because of fighting.
Thousands returned to the camp on Thursday despite sporadic gunfire.
On Wednesday, Palestinian president Mahmud Abbas urged the international community to help those refugees fleeing fighting in camps in Syria to enter the West Bank and Gaza.
The fate of Palestinian refugees and their descendants is one of the most sensitive issues in negotiations between Israel and the Palestinians.
It remains an emotive issue for Palestinians more than 60 years after many first fled during what they call the "Nakba" or "catastrophe" of their exodus during the fighting that followed Israel's creation in 1948.
Around 760,000 fled or were forced from their homes during that time, followed by several hundreds of thousands more who left during the 1967 Six-Day War in which Israel captured east Jerusalem, the West Bank and Gaza.
The Palestinian Central Bureau of Statistics earlier this year put the Palestinian population living in the Palestinian territories at 4.29 million, with 2.65 million in the West Bank, including east Jerusalem, and 1.64 million in Gaza.
Another 1.4 Palestinians live in Israel and are often referred to as Arab Israelis. They have citizenship and now make up 20 percent of the Jewish state's population.
Hundreds of thousands live in countries throughout the world, with large communities in the United States and several countries of Latin America.
According to the United Nations Relief and Works Agency (UNRWA), there are another five million Palestinian refugees and their descendants in the Middle East.
The number includes 850,000 in the West Bank, 1.2 million in Gaza, two million in Jordan, 525,000 in Syria and 450,000 in Lebanon.
Their living conditions and rights differ vastly from place to place, with Jordan the only Arab country to grant the population nationality.
In Lebanon, many professions are off-limits to Palestinians, who live in difficult conditions in refugee camps. Their situation in Syria had been comparatively comfortable, before the outbreak of violence in the country.
Palestinians are also present throughout much of the Gulf, where they began moving in the 1960s lured by the opportunity of employment.
The right of return for Palestinian refugees remains a key issue in peace negotiations with Israel.
UN General Assembly Resolution 194, adopted on December 11, 1948, stipulates that "the refugees wishing to return to their homes and live at peace with their neighbours should be permitted to do so at the earliest practicable date."
It says that compensation should be paid for the property of those who do not want to return.
The Palestinians -- backed by the Arab world -- want Israel to recognise the principle of the right of return, with a detailed solution to be negotiated subsequently.
But Israel fears that this would open the door for a massive influx that could chance its character as a Jewish state.