More than 250 children have been shot with live bullets since the end of March in the Gaza Strip following the escalation of protests in the area, the worldwide aid organization Save the Children said in a statement on Friday.
Holding Palestinian flags and banners, the protesters were chanting "Free Palestine", "Freedom Now" and "End Occupation" slogans.
The first "U.S. Embassy" road signs went up in the nation's capital earlier this week in anticipation of the move, a promise kept by Trump though several U.S. presidents had made the same assurances before.
Reports emerged on Friday morning that Israeli forces had already begun heavily firing tear gas at the crowds in some areas, while one protester was shot with a live bullet east of Gaza City. Fifteen protesters were wounded by live fire, four of them seriously, including a 16-year-old boy shot in the head, Gaza health officials said.
Soldiers are using dispersion methods and opening fire according to the rules of engagement, the spokesman said.
The 40-year-old Palestinian was killed in the seventh consecutive week of protests on the border of the coastal enclave.
Also on Friday, Haniyeh noted "What the Palestinian resistance has in the Gaza Strip is terrifying for Israel", referring to the Palestinian resistance's steadfastness in the face of Israeli wars and siege and its decision not to give up its arms, but to develop it.
Rioters near the border fence with Israel reportedly threw grenades, pipe bombs, and rocks at soldiers.
Friday's protest comes just three days ahead of what the Hamas leader of Gaza says will be a march by tens of thousands who could burst through the border fence into Israel.
US President Donald Trump's recognition of Jerusalem as Israel's capital infuriated Palestinians, who see the eastern part of the city as the capital of their future state.
Since the "Great March of Return" protests began on March 30, no Israelis have been injured.