At least 17 Palestinians were killed and dozens injured in clashes between Israeli forces and Palestinian youth on Saturday, Palestinian medical sources said.
The army said in a statement that it fired rubber-coated steel bullets and tear gas to disperse protesters, but witnesses and Palestinian sources disputed the figures.
“The death toll has been raised to 17.
We must all come together to stop this massacre, this killing,” Palestinian President Mahmoud Abbas said.
An Israeli military spokeswoman said Israel was looking into the reports of civilian casualties.
“There is no reason to doubt the figures as Israel is following the instructions of our commanders,” said the spokeswoman, Lt Col Anna Silber.
The Palestinian Health Ministry also reported the deaths.
“We are reporting that 16 civilians were injured in the clashes between the Israeli forces, and we are checking the numbers,” said Ashraf al-Qudra, the ministry’s director of information and public relations.
The violence began after a protest in the Old City of Hebron on Saturday night, in which at least nine Palestinians were injured.
The clashes began when protesters set off fireworks at a nearby gas station and set off a fire at a car.
The Israeli military said the fire was put out by the protesters, and that Israeli forces responded with live fire.
The soldiers fired rubber bullets and stun grenades to disperse the protesters.
Some of the wounded, however, remained in intensive care.
The protests have become increasingly violent in recent months as Palestinian frustration with the slow pace of peace talks and the military-imposed blockade of Gaza have grown.
Israel has also been targeting the Islamist Hamas movement.
It has been fighting a deadly war with Hamas, which has been waging a four-year war with Israel in the Gaza Strip.
In the latest escalation, a Palestinian protester was killed by Israeli forces in the northern West Bank city of Nablus on Sunday.
The police officer was reportedly shot and killed after an attack on his vehicle.
Hamas has denied any involvement in the attack.
Israeli authorities have launched a wide-ranging crackdown on the group.
Israeli soldiers have also clashed with Palestinians in the occupied West Bank, in the latest flare-up over the occupation of the Palestinian territories.
Palestinian officials and human rights groups have accused Israel of targeting civilians in the West Bank and Gaza, which the Palestinian Authority has controlled since the 1967 Middle East war.
Palestinians say Israel has used the pretext of security to target Palestinian civilians and civilians in Gaza and the occupied territories, and are calling for an end to the occupation.
“These are violations of international law, which have been repeatedly and consistently ignored by the international community,” Amnesty International’s deputy director, Nabil Abu Rdainah, told Al Jazeera.
“They violate international law when they are targeting civilians.
This is an attack against the Palestinian people, an attack that is completely unjustifiable and completely disproportionate.”