Two Palestinian teenagers were killed on Friday in a blast in Gaza City which was thought to be caused by an unexploded Israeli tank shell, medical and security sources said.
The two died when the device exploded in the city's Shuja'iyeh neighbourhood, security sources said.
They said the shell was most likely left over from Israel's 22-day war against Gaza, dubbed "Operation Cast Lead", which began at the end of December 2008 and cost the lives of 1,400 Palestinians, most of them civilians, and 13 Israelis, 10 of them soldiers.
The two teens, both of whom were 16, were identified as Mumen Hilles and Muntasser al-Batniji.
The army claimed it was not aware of any such incident.
Earlier, another three Palestinians, one of them a teenager, were wounded by Israeli gunfire in two incidents near the border, medical and security sources said.
Two of them, both in their 20s, sustained gunshot wounds to their legs while collecting building material in an area near the northern town of Beit Lahiya, medical sources told AFP.
Further south, a 16-year-old boy was shot in the leg near his home in Khuza'a, a village east of the city of Khan Yunis and close to the border, security officials said.
The Israeli military confirmed the shootings, saying troops had in both cases opened fire towards their legs after they failed to heed warning shots.
Israeli troops often fire towards people in the border zone, particularly in northern Gaza where Palestinian youngsters try to make money by scavenging gravel.