Jerusalem (AFP) - Israeli warplanes struck multiple militant targets in the Gaza Strip early Thursday in response to Palestinian rocket fire, but nobody was injured according to Palestinian security sources.
They said that the raids hit three training bases of the Ezzedine al-Qassam brigades, the military wing of Hamas, in Gaza City and a fourth in the southern city of Khan Yunis.
The rocket fire was claimed by a group calling itself Supporters of the Islamic State in Jerusalem which recently emerged in the Gaza Strip.
It said the attack was to avenge the death of a radical Islamist in Gaza this week.
An Israeli military statement confirmed the air strikes but did not identify the targets.
"Yesterday, June 3, 2015, two rockets were launched at southern Israel from the Gaza Strip," it said, adding that they fell on open ground near the southern city of Ashkelon and the town of Netivot. "No injuries were reported."
"In response to this attack, the Israel Defence Forces struck three terror infrastructures in the Gaza Strip," it said.
Defence Minister Moshe Yaalon blamed the territory's de facto rulers Hamas for the rocket fire.
"We will hold Hamas responsible for everything that happens in the Gaza Strip and we will not tolerate any attempt to harm our citizens," he said in a statement.
"We will not compromise the security of Israeli citizens and we will not accept a return to a situation of regular fire (from Gaza)."
Israel has a general policy of holding Hamas responsible for every rocket attack from the territory under its control, no matter which group actually launched it.
On Wednesday night Israeli police reported that three rockets were fired but that patrols were searching to find where they had fallen.
Israeli public radio said the latest volley could be related to internal Gaza infighting between Hamas and its extremist opponents.
Hamas security officials shot dead local Salafist leader Yussef al-Hanar on Tuesday after he tried to flee following a confrontation at his house, the interior ministry said.
Some witnesses said he belonged to a group affiliated with IS.
The incident came as Hamas stepped up measures against militants belonging to Islamic extremist groups.
Salafists are Sunni Muslims who promote a strict lifestyle based on that of early "pious ancestors".
In Gaza they have made no secret of their disdain for Hamas over its observance of a tacit ceasefire with Israel and its failure to implement Islamic law.
Since last summer, when Israel and Hamas fought a deadly 50-day war in and around Gaza, there have been growing signs of internal unrest between Hamas security forces and extremist splinter groups.