Palestinians clashed with Israeli forces in the occupied West Bank on Wednesday during demonstrations to mark 65 years since what they call the Nakba (Catastrophe) when the creation of Israel's caused many to lose their homes and become refugees.
A shell fired from Gaza, which is ruled by the Islamist movement Hamas, exploded in an open area of Israel but caused no injuries, according to an Israeli military spokesman. There was no immediate claim of responsibility.
U.S. Secretary of State John Kerry is to return to the region on Tuesday in another bid to revive peace talks frozen since 2010.
But a resolution remains elusive and many Palestinians want refugees and their descendants to return to lands now in Israel - an idea Israel rejects, saying it would spell the end of the Jewish state.
Protesters skirmished with Israeli forces outside a refugee camp near the West Bank city of Hebron and at a prison near Ramallah. Several Palestinians were injured.
Israeli police in Jerusalem scuffled with Palestinian protesters, tossing stun grenades and making several arrests.
Thousands also rallied in the main square of Ramallah, the Palestinian de facto capital while Jerusalem remains under Israeli control, holding up placards with the names of villages depopulated in 1948 and old keys, symbols of lost homes.
"For the sake of my future and to return to my family's land, I don't want any more useless negotiations but the path of resistance and the rifle," said Ahmed al-Bedu, a gangly 15-year-old Palestinian who holds Jordanian citizenship.
Israel declared independence on May 14, 1948 on the eve of the end of British rule over Palestine, and neighbouring Arab armies invaded in a sharp escalation of fighting already raging between Jews and local Arabs. Five months earlier, the United Nations had adopted a plan to partition Palestine into Jewish and Arab states, a blueprint rejected by Arabs.
5.3 million registered refugees
Many Arab residents fled or were expelled by force from their homes and prevented from returning. Only Jordan, which now has a peace treaty with Israel, gave the refugees citizenship.
According to official Palestinian figures published this week, 5.3 million Palestinians - almost half of their total number in the world - are registered by the United Nations as refugees in Syria, Lebanon, Jordan, the West Bank and Gaza.
Many of them live in the concrete warrens of overcrowded camps, with poor access to employment and basic services.
Mahmoud Abbas, president of the Western-backed Palestinian Authority and himself a refugee from a town now in northern Israel, stoked Palestinian outrage last year by telling an Israeli news channel he did not seek to return home.
Saeb Erekat, Abbas's top negotiator with Israel, said on Wednesday that sectarian conflicts in Syria and Iraq endangered Palestinians there and that Israel's "refusal to assume responsibility for the refugee question" and to agree on a "just solution" for them was harming prospects for peace.
The Palestinian Authority seeks an independent state in the West Bank and Gaza Strip with East Jerusalem as its capital - all lands captured by Israel in the 1967 Middle East war. Israel deems Jerusalem its "eternal and indivisible" capital.
Hamas rejects Israel's existence and refuses to renounce violence against it, saying a return of refugees can be attained only through armed force.
"Any initiatives and solutions that do not secure the return of our full rights will be rejected by our people. Our holy land is not for sale or bargain," the group said in a statement.
"Resistance by all its forms, and foremost armed resistance, will remain our way to extract our rights."
(Additional reporting by Ali Sawafta and Nidal al-Mughrabi; Editing by Mark Heinrich and Robin Pomeroy)