"As of now, 36 rocket launches were identified from Gaza towards Israel", the army tweeted.
Sirens wailed in southern Israel warning of incoming projectiles from Gaza and Israeli media reported two people were lightly injured from shrapnel in the border town of Sderot.
An Israeli policeman surveys the scene where a rocket exploded in the southern city of Sderot, Israel August 8, 2018.
A 30-year-old Hamas affiliate was killed in the strikes, the Gaza Health Ministry spokesman Ashraf al-Qedra said.
Israel initially said the two fighters were shooting at Israeli soldiers, but Hamas said they were involved in a training exercise that senior officials were attending.
In return for calm in Gaza, Israeli officials said on Sunday they would reopen a commercial border terminal that had been shuttered in response to damage caused by fires set by burning Palestinian kites and balloons lofted over the frontier.More news: Boris Johnson under mounting pressure to apologize for controversial burqa comments
The flare-up comes as Egypt is trying to broker a long-term ceasefire between the two sides.
Three Palestinians, including a pregnant woman and her toddler daughter, were killed and 11 others were injured in Israel's retaliatory strikes in Gaza, the enclave's Hamas-run health ministry said in a statement.
A fireball exploding during Israeli air strikes in Gaza City.
Israeli fighters also struck a tunnel on the Mediterranean coast and targeted weapons and rocket manufacturing sites, as well as a military complex serving as a central logistic warehouse, the IDF noted.
The attacks came after around 150 rockets were fired from Gaza into the occupied territories from late Wednesday into Thursday, the Israeli military added.
The majority of the rockets hit open areas while four were intercepted, it said.More news: Liverpool finish pre-season by beating Torino
"Defense Minister Avigdor Liberman reassured the mayor of Sderot and the heads of the regional councils in the vicinity of the Gaza border that "we will do what needs to be done" to restore calm to region".
The gathering had raised hopes a deal for a lasting truce with Israel, with the backing of Egypt and the United Nations.
On Thursday, the IDF destroyed a five-story building allegedly housing Hamas' internal security service and offices of the group's senior officials.in response to a rocket fired at Beersheba, almost 40km from the border with Gaza.
Both the United Nations and Egypt have not publicly discussed their plans for a renewed Gaza ceasefire, but have said it would bring economic relief to Gaza's two million residents experiencing shortages under crippling blockades. The protests have been aimed in part at trying to break the blockade.
Israeli forces also began massing on the Gaza periphery, and the officer who spoke to Army Radio said a ground operation was very likely if the situation continued to deteriorate.
The statistics showed that 155 Palestinians were shot and killed, while 17,259 suffered from various injuries, including tear-gas suffocation. Our strong commitment to the State of Israel's right to defend its borders and civilians is uncompromising.More news: Conor McGregor's Lawyer Hints At Date And Location For Khabib Fight