Israeli air strikes on Wednesday killed a Gaza teenager and a militant who the army said was a "global jihad" operative behind a deadly ambush on Israel's border with Egypt.

The two deaths raised to eight the number of Palestinians killed in three days of bloodshed in and around Gaza, while militants have fired scores of rockets at the Jewish state, one of which scored a direct hit on a border police outpost, wounding four.

On Wednesday evening, two Palestinian youths were wounded in an airstrike on a Hamas training site in northern Gaza. A second attack at another Hamas training camp in Nuseirat in the centre of the territory left no casualties.

The Israeli military said its aircraft "targeted two terror sites in the northern Gaza Strip. Direct hits were confirmed."

"The targeting is in response to over 75 rockets that were fired at Israel during the past three days," it said.

An earlier strike hit a farm in the Zeitun neighbourhood, just east of Gaza City, killing 14-year-old Moamen al-Adam and seriously wounding his father, medics said. Another two people were also wounded.

An Israeli military spokeswoman told AFP that "during the day, rockets were fired at Israel from a populated civilian area in the northern Gaza Strip."

"This afternoon Israeli army aircraft targeted a rocket launching squad in this area," she said.

Earlier on Wednesday, a missile strike on a motorcycle in the southern border city of Rafah killed 21-year-old Ghaleb Ermilat, whom locals said was a militant of the Islamist movement Hamas which rules the territory.

The Israeli military said he was a "global jihad operative" who was behind a deadly ambush along the Israeli-Egyptian border on Monday morning that killed an Israeli civilian and sparked a firefight in which two of the gunmen were killed.

A third is believed to have fled back to Sinai.

The army said that besides Ermilat, another "global jihad terror operative" involved in Monday's ambush was seriously wounded in the raid, naming him as Mohammed Rashdan, a Rafah resident born in 1984.

It said Ermilat and Rashdan were members of Tawhid wal Jihad, a "global jihad terror movement, that is responsible for ongoing terror attacks against Israeli civilians and soldiers."

"Rashdan's terror activities included weapon transfers, supplying explosive devices to terror operatives, firing rockets at Israel, sniper and mortar fire, and smuggling terror operatives to and from Gaza," the army said in a statement.

Ermilat and Rashdan had planned the ambush and were "actively involved in planning another attack," it said.

On Tuesday, a previously unknown Islamist group claimed responsibility for the ambush in a video carried by a US-based monitoring service, SITE Intelligence.

Made by the "Mujahedeen Shura Council in the Environs of Jerusalem," the clip showed two gunmen standing in front of Al-Qaeda's black flag saying they were poised to carry out an attack against Israel.

One claimed to be from Egypt, while the other said he was from Saudi Arabia.

Meanwhile, there was no let-up in the violence around Gaza on Wednesday, with at 39 rockets and mortars hitting the Jewish state, causing damage to several buildings.

A police spokeswoman told AFP that eight people were being treated for shock.

Overnight, the air force carried out seven raids, with Palestinian security sources saying they had hit a training centre used by Hamas militants and several naval police outposts.

In total, 45 rockets hit Israel on Tuesday, with one scoring a direct hit on an Israeli border police outpost north of Gaza.

All 45 rockets were claimed by the Ezzedine al-Qassam Brigades, the armed wing of Hamas, in a rare show of force. Previously, the group had been observing a de facto truce on rocket attacks.

As the violence rumbled on, a senior Gaza official told AFP that Egypt was in contact with Israel and the militant groups in a bid to restore calm.

"The Palestinian factions are ready to return to the calm as long as Israel stops its attacks," he said, speaking on condition of anonymity.

Giora Eiland, Israel's former national security adviser, said he believed Hamas would "find a way to calm things down ... in the next two or three days after proving to the other factions that it is capable of acting against Israel."

"Neither Hamas nor Israel has any interest in provoking an escalation in the short term," he told public radio.