Gaza (CNN) -- Angry clashes erupted Friday in the West Bank, after Palestinian leaders called for a "day of rage" in response to the shelling of a United Nations shelter that killed 16 people.
At least four Palestinians were killed in outbreaks of violence in several parts of the West Bank, according to medical sources.
The call for a massive follow-up to what were already some of the largest West Bank protests in years came as diplomats scrambled to find a cease-fire proposal that would satisfy mortal enemies Israel and Hamas and end more than two weeks of violence that has claimed more than 800 lives, most of them civilians.
The developments come as Israel and Hamas agreed to a 12-hour humanitarian cease-fire beginning Saturday morning.
Prime Minister Benjamin Netanyahu told U.S. Secretary of State John Kerry that Israel agreed to a cease-fire beginning Saturday at 7 a.m. local time, a U.S. official told CNN. The official, who is traveling with Kerry, spoke on condition anonymity. The news was first reported by Reuters and Agence France Presse.
Hamas also agreed to the cease-fire, according to a statement released by senior Hamas spokesman Sami Abu Zuhri.
The agreement came hours after U.N. Secretary-General Ban Ki-moon called for the cease-fire, with the hopes it would be extended to seven days, while diplomats work to broker an end to the bloodshed.
The cease-fire talks are playing out against a backdrop of mounting casualties.
At least 864 people have been killed and more than 5,700 wounded since the start of an Israeli operation on Gaza, the Palestinian Ministry of Health said Friday. An Israeli military representative said Friday that another soldier had been killed in Gaza, bringing the total number of Israelis killed to 36 -- 33 soldiers and three civilians.
A 23-year-old man was shot near Huwara village outside Nablus by Jewish settlers, a doctor at the Rafidia Hospital said. The circumstances of his death are unclear, but it led to clashes between protesters and the Israeli military in which another man was killed, medical sources said.
Two more men were killed during clashes with Israeli troops at a checkpoint north of Hebron in Beir Ummar in the West Bank, according to Palestinian medical sources.
A pro-Hamas demonstration in Ramallah drew a crowd of several hundred, and a protest march toward a Jewish settlement led to heavy clashes with the Israel Defense Forces and border police.
Several people were injured, a CNN crew at the scene said.
The IDF confirmed one Israeli soldier was killed and several were wounded Friday in Gaza, when militants fired mortars and anti-tank missiles.
It also confirmed one of its soldiers, Sgt. Oron Shaul, was killed in battle in Gaza on Sunday.
Hamas had said it was holding Shaul after capturing him in an ambush on an armored personnel Sunday in which six other IDF soldiers died.
A committee led by the chief rabbi of the IDF concluded that he should be defined as "a soldier killed in action whose burial site is unknown," an IDF statement said.