The 15-year-old boy, Muhammad Abu Salha, was killed in the northern West Bank town of Nablus. His body was discovered by his family after Israeli troops left the area.
Three other Palestinians were wounded by Israeli gunfire in two separate incidents.
According to the Israeli army, the teenager and at least two others had been planting a bomb.
Nablus residents heard a loud explosion earlier, thought to have been caused when the bomb went off prematurely, before Israeli soldiers went to the scene and opened fire, security sources said.
Two 15-year-old boys, one with a gunshot wound to the stomach and another with a bullet in the leg, were taken to a Nablus hospital.
An Israeli army spokeswoman said soldiers opened fire at Palestinians planting an explosive device outside Nablus just as an army patrol was to pass down the road. Soldiers identified "several hits", she told AFP.
Further north, a resistance fighter from the armed wing of the Islamic Jihad movement was seriously wounded when Israeli occupation soldiers opened fire on his car near the town of Tubas, medical and army sources said.
Samir al-Ghul, a 26-year-old member of the Al-Quds Brigades, was being treated in hospital with serious stomach wounds after being hit near a checkpoint just outside the town, 10km north of Nablus.
The soldiers opened fire after al-Ghul failed to stop, the security sources said.
Abu Salha's death brings to 4880 the number of people killed since the start of the second Palestinian intifada (uprising) in September 2000. More than three-quarters of the victims have been Palestinians.