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.
@highlight
NEW: Israel Defense Forces warn if militants attack during truce, it will respond
@highlight
Israel and Hamas agree to 12-hour humanitarian cease-fire
@highlight
At least four people are dead as new protests, violence, break out in the West Bank
@highlight
The Israeli military confirms the death of a soldier that Hamas claimed to have captured
A @placeholder government statement called the shelling "Israeli brutal aggression."