Palestinians are marking Nakba Day, or the "day of catastrophe", commemorating Israel's declaration of statehood in 1948 and the displacement of hundreds of thousands of their kin from their land and homes.
Protests were scheduled to take place across the Palestinian territories on Tuesday with the main rally planned in Ramallah in the occupied West Bank. Demonstrations were also expected at the nearby Ofer military prison and Qalandia checkpoint where there has been some minor clashes.
Our correspondent Cal Perry in Qalandiya said: "the clashes are very small and very fierce, the Israeli's have been firing rubber bullets and tear gas throughout the morning.
"The crowd is expected to grow throughout the day. we are expecting to see things in Jerusalem, and Qalandia because its the crossing between Jerusalem and Ramallah."
A mass rally is scheduled to take place in the Gaza Strip, with smaller protests to be held elsewhere in the West Bank and East Jerusalem.
The Higher Arab Monitoring Committee, which represents Palestinian communities in Israel, has called for a general strike and for Palastinians to visit the sites of former Palestinian villages.
More than 760,000 Palestinians, estimated today to number 4.7 million with their descendants, fled or were driven out of their homes.
About 160,000 Palestinians stayed behind, and now number about 1.3 million, or 20 per cent of the population of Israel.
Early on Tuesday, an AFP correspondent said clashes broke out between police and demonstrators in the East Jerusalem neighbourhood of Issawiya.
Israel also said a projectile fired from Gaza landed in the country's south, though it was unclear if it was linked to the Nakba commemoration.
"An explosive device fired from the Gaza Strip, a rocket or a mortar shell, landed early this morning in southern Israel, causing no injuries or damage," Micky Rosenfeld , Israeli police spokesman, told AFP.
Israeli security forces are on alert ahead of the main Nakba Day commemorations, which have in the past often resulted in clashes with troops and police.
"We are coordinating with the military and border police, we hope things will be quiet," Rosenfeld said on Monday. "We have mobilised a number of units in various areas," he said, without elaborating.
Last year, Israeli troops opened fire on demonstrators from Lebanon and Syria as they tried to breach a security fence and enter Israel.
Four protesters from Syria were killed along with another 10 from Lebanon.
A senior military official in Israel's northern command said troops had trained to handle all situations, although they were not aware of plans for any big demonstrations along the borders.
"We are getting ready for all kinds of provocations," he told AFP on condition of anonymity.
This year's Nakba events come with protesters hailing a mass hunger strike by Palestinian prisoners in Israeli jails.
The strike appeared to have come to an end on Monday night after an Egyptian-mediated deal under which Israel offered a number of measures easing prison conditions in exchange for an end to the hunger strike.