Israeli forces have killed 56 people since 2005 in clashes with rock-throwing Palestinians, said B'Tselem, which accused the military of having "extensively and systematically violated" rules barring deadly retaliation for non-lethal assault.
"The Israeli military's standing orders explicitly state that live ammunition may not be fired at stone-throwers," it said.
Last week, Israeli forces shot dead two Palestinians from Bethlehem.
On Wednesday, 15-year-old Salih al-Amarin, from Azza refugee camp, died in hospital after Israeli forces shot him in the head during clashes in Bethlehem a few days earlier.
The same day, Lubna Hanash, 22, was shot in the head when Israeli soldiers in a civilian car opened fire at a group standing at the entrance to al-Arrub refugee camp south of Bethlehem.
The Israeli army said the B'Tselem report "presents a biased narrative, relying primarily on incidents that are either old or still under investigation by the Military Police."
"The (army) does everything in its power to ensure that the use of riot dispersal means is done in accordance with the rules of engagement," the military said in a written response sent to Reuters.
Of the Palestinian fatalities since 2005, six were killed by rubber-coated metal bullets and two by teargas canisters, both supposedly non-lethal weapons which were fired directly at protesters, B'Tselem said.
"In practice, members of the security forces make almost routine use of these weapons in unlawful, dangerous ways, and the relevant Israeli authorities do too little to prevent the recurrence of this conduct," the report said.
The other 48 protesters killed where hit by live ammunition, according to the group.
RAMALLAH (Reuters) -- Israel is breaking its own rules of engagement by using deadly force to disperse unarmed Palestinian protesters in the occupied West Bank, the Israeli rights group B'Tselem reported on Monday.