Hundreds of people were on Wednesday holding a series of rallies in Gaza to mark "Land Day," kicking off a day of protest by Arab Israelis and Palestinians.
Witnesses said hundreds of people waving banners and holding up pictures of Palestinian prisoners in Israeli jails had joined a sit-in near the northern town of Beit Lahiya for a demonstration called by the various factions.
And in Gaza City, hundreds of students began a protest march at Al-Azhar University but were stopped by Hamas police, who arrested a number of them, witnesses said, without saying how many.
Protesters were also gathering in the West Bank city of Ramallah.
The rallies kicked off a day of demonstrations which are to take place across Israel and the Palestinian territories to mark Land Day, recalling an incident in 1976 when Israeli troops shot and killed six people during protests against land confiscations.
In Israel, demonstrators were expected to gather for the main rally in the northern Galilee town of Arrabeh, which was to start at 2:00 pm (1200 GMT) and be attended by Arab Israeli MPs and leaders of the Higher Arab Monitoring Committee.
Many Arab Israeli schools were closed for the day, and Arab rights groups said shops and businesses in Sakhnin were observing a one-day general strike to mark the anniversary.
Further south, another rally was to take place in Al-Araqib in the Negev, a Bedouin village that has been levelled several times by the Israeli police over the past eight months.
Israel has never recognised Bedouin claims of land ownership in the Negev and wants the population to relocate into seven government-planned townships.
Israel's Arab minority leads Land Day demonstrations every year to protest against discrimination and assert its solidarity with the Palestinians.