Wasel Abo Youssef, a member of the umbrella Palestine Liberation Organization (PLO), said 100,000 Palestinians have been killed and one million detained since the Nakba.
"Today, the Palestinian people affirm that they will not forget their sacred right to return," he added.
The Palestine-Israel conflict dates back to 1917 when the British government, in the now-famous Balfour Declaration, called for "the establishment in Palestine of a national home for the Jewish people".