Palestinian boys at Isawiya riots (Photograph: Marc Israel Sellem) Yassam riot police in Isawiya (Photograph: Marc Israel Sellem) Israeli security forces line up at Isawiya (Photograph: Marc Israel Sellem) Palestinian fires sling shot in Isawiya (Photograph: Marc Israel Sellem) Palestinian man arrested in Isawiya (Photograph: REUTERS/Ammar Awad) Palestinians take part in a rally marking Nakba in the West Bank (Photograph: REUTERS/Mohamad Torokman) Palestinian supporters in front of the UN headquarters (Photograph: REUTERS/Mohamad Torokman) Rally marking Nakba in Gaza City (Photograph: REUTERS/Mohammed Salem) Stone-thowers, police clash at Isawiya (Photograph: REUTERS/Ammar Awad)

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Khaled Abu Toameh contributed to this report.

Three Border Police officers and one IDF officer were lightly injured in "Nakba Day" protests at the Kalandiya checkpoint near Jerusalem and at Beitunia near the Ofer Prison on Tuesday. Dozens of Palestinians were injured in clashes that were still taking place, although the protests and events appeared to be much calmer than the previous year.Hundreds of Palestinians protested at the two crossings, some throwing stones and Molotov cocktails. IDF and police forces responded with tear gas, rubber bullets and other crowd dispersal tools.Events marking Nakba Day (the Day of Catastrophe marking the anniversary of the establishment of Israel and the creation of the Palestinian diaspora), including rallies and demonstrations, took place at various locations in the West Bank, Gaza Strip and east Jerusalem as well as a number of neighboring Arab countries.In the late morning Tuesday, thousands of Palestinians gathered in Ramallah for a major rally at the Martyr Yasser Arafat Square. The protesters raised black banners and Palestinian flags to mark the event. Palestinian Authority Prime Minister Salam Fayyad was in attendance.Throughout the West Bank, the PA suspended work and studies to allow the participation of as many Palestinians as possible in the protests and rallies.Hundreds of Palestinians threw stones and firebombs outside the Ofer Prison adjacent to the Beitunya crossing and IDF and police forces responded with tear gas, rubber bullets and other crowd dispersal means. Approximately 20 Palestinians were injured, according to Army Radio.At the Kalandiya checkpoint between Jerusalem and Ramallah, some 300 Palestinians protested, a number of whom clashed with security forces. At least 20 Palestinians were injured in the incident.In east Jerusalem's Isawiya neighborhood, police arrested four people on suspicion of throwing stones. In that incident, children as young as five years old were seen participating in the violence against security forces.In the Gaza Strip, representatives of Hamas, Fatah and other Palestinian political factions held a joint rally to mark Nakba Day. The organizers had called on Palestinians to gather in the center of Gaza City and march toward UN headquarters in the city.Earlier Tuesday morning, Palestinians threw stones at Israelis praying at Rachel's Tomb near Bethlehem. Police dispersed the attackers. There were no injuries in the attack.At a checkpoint near the Jewish settlement in Hebron, Palestinians hurled stones at security forces. IDF soldiers and Border Police dispersed the riots. No damages or injuries were reported.The IDF also raised its alert level on the Syrian and Lebanese borders in preparation for potential violence. Last year's Nakba Day was marred by at least a dozen deaths as people were shot trying to rush Israel’s northern borders.