“We condemn the killing of the child Zaki Hopi by Egyptian army gunfire on the borders, we consider what happened as a dangerous development and excessive use of force,” the Islamist organisation said in a statement.
“What happened is not appropriate to neighbourly relations between brothers.”
Gaza emergency services spokesman Ashraf al-Qudra said that Hopi was 17 years old and not 23 as previously stated.
He was killed in the Gaza frontier town of Rafah by Egyptian soldiers firing from across the border, Qudra said, although the motive was not immediately clear.
The border troops shot Hopi “in the back and the bullet settled in the heart. He died on the spot,” he told AFP.
Hopi is the first Palestinian “to have been killed in a long time” along the border between the Gaza Strip and Egypt, according to Qudra.
Egypt announced on Tuesday that work to double the width of a buffer zone along the Gaza border would begin next week to prevent militants infiltrating from the Palestinian enclave.
Construction of the 500-metre (550-yard) buffer zone along 10 kilometres (six miles) of the border comes after an October 24 suicide bombing that killed 30 Egyptian soldiers. Some 800 homes are being demolished in the process.
After that incident, Egypt declared a three-month emergency in parts of North Sinai — a remote but strategic region bordering Israel and Gaza — and closed the Rafah border crossing for two months.
The crossing is Gaza’s only gateway to the outside world not controlled by Israel.
Egypt suspects Palestinian militants of aiding jihadist attacks against its security forces, which have increased since the army ousted Islamist president Mohamed Morsi last year.
The Egyptian army has also stepped up the destruction of tunnels from Gaza it says are used to smuggle arms, food and money by Palestinian militant group Hamas which controls the territory.
Cairo says it has destroyed more than 1,600 tunnels since Morsi’s ouster. (AFP)