Protesters and Israeli forces clashed in the West Bank on Wednesday as thousands of Palestinians commemorated the Nakba (catastrophe) of the Jewish state's creation in 1948, during which 760,000 Palestinians fled their homes.
Soldiers fired rubber bullets at protesters gathered in front of Ofer military prison near Ramallah, wounding 15 of them, Palestinian medical officials said.
Demonstrators pelted soldiers with stones, the army said.
In east Jerusalem, police clashed with demonstrators outside the Old City's Damascus Gate, police spokeswoman Luba Samri told AFP
Protesters threw stones at police, injuring three of them, while security forces responded with stun grenades, water hoses and horses to disperse the demonstrators, she said.
Clashes subsided by Wednesday night, with 27 Palestinians arrested, Samri added, eight of them for attacking Jews in and near Jerusalem's Old City.
Thousands of Palestinians took to the streets in the West Bank and the Gaza Strip to demonstrate on Nakba Day and assert their "right to return" to where their ancestors fled after the Israeli victory over Arab armies.
Protesters held aloft Palestinian flags and replicas of the keys to the houses their families abandoned in 1948.
Some 1,000 people turned out in the northern West Bank town of Nablus, and another 300 in southern Hebron.
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Palestinians threw a petrol bomb at an army jeep near Hebron, burning the vehicle out completely and wounding four soldiers inside it, an army spokeswoman told AFP.
In Hamas-ruled Gaza, thousands of people gathered in the centre of Gaza City, holding placards that read "We will get back to Palestinian villages and towns, no matter how long it takes" and "The right of return is sacred and inalienable".
Earlier in the day, Gaza-based militants fired a projectile that landed in an open field in southern Israel, causing no damage or casualties, police said.
A military spokeswoman could not say whether the projectile was a mortar shell or rocket. No group immediately claimed responsibility for the incident.
Over the past two months, there has been an uptick in rocket fire on southern Israel after more than three months of complete quiet that followed a deadly confrontation in November that ended with an Egyptian-brokered truce.
In Ramallah, where the Palestinian Authority is based, sirens sounded for 65 seconds, representing the 65 years of the existence of the modern state of Israel.
In a televised speech on Tuesday evening, Palestinian president Mahmud Abbas said "there is no country in the world, including the United States of America, that denies our right to establish our independent state based on the 1967 borders" -- a reference to land occupied by Israel since the Six Day War.
"We are today a number (of people) and a truth that cannot be overlooked," he said.
In 1948, more than 760,000 Palestinians -- estimated today to number more than five million with their descendants -- fled or were driven out of their homes.
Around 160,000 Palestinians stayed behind and are now known as Arab Israelis. They and their descendants number about 1.3 million people, or some 20 percent of Israel's population.