Israel and Gaza have traded heavy fire as hopes faded of securing a truce to end days of fighting that have killed dozens of Palestinians.
At least 33 Palestinians have been killed, Gaza's health ministry said on Friday. Those killed included militants but also children.
The violence has been met with international calls for de-escalation, with the European Union pushing for an "immediate comprehensive ceasefire".
Israel announced it was "striking Islamic Jihad targets" in the densely populated Palestinian territory, while AFP news agency's journalists saw air strikes hit Gaza.
Sirens warning of incoming fire meanwhile rang out in Israeli communities close to the border with Gaza, as well as blaring in an Israeli settlement near Jerusalem in the occupied West Bank.
Violence broke out on Tuesday when Israel killed three top members of the Islamic Jihad group, while subsequent strikes have killed at least three other senior figures.Continued Israeli aggression
A high-ranking commander, Iyad al Hassani, was killed in a strike on a Gaza City apartment Friday, a spokesman for the group told AFP.
Hours earlier, Islamic Jihad said the latest rocket fire was a "response to the assassinations and the continued aggression against the Palestinian people".
The launches, witnessed by AFP journalists, came after a rocket killed one civilian in the central Israeli city of Rehovot on Thursday night.
Daily life in the coastal territory, ruled by Hamas, has largely come to a standstill, while Israel has told its citizens near Gaza to stay close to bomb shelters.
In Gaza's central Deir al Balah area, farmer Belal Basher stood beside the ruins of the home he said was hit by multiple Israeli strikes.
"Our situation is the same as that of any Palestinian citizen whose house is targeted and whose dream, built over the years, is destroyed," the 33-year-old told AFP.
Earlier, there had been cautious optimism a truce may be nearing, with an Islamic Jihad source saying a deal drawn up by Cairo had been circulated among the group's leadership.
But the source subsequently said Israel was "disrupting Egypt's efforts for a ceasefire".
Over 100 Palestinians wounded
The decision to renew air strikes on Gaza this week was authorised by Israeli Prime Minister Benjamin Netanyahu, who returned to power in December alongside extreme-right and ultra-Orthodox Jewish allies.
The violence has wounded more than 110 people in Gaza, according to the latest health ministry toll.
Israel's Magen David Adom emergency services has treated five people who were hit by shrapnel or glass, or suffered blast injuries from the rocket fire.
This week's escalation is the worst since August, when 49 Gazans were killed in three days of fighting between Islamic Jihad and Israel.
At least 19 of those were children, according to the United Nations, while rocket fire wounded three people in Israel.
An Israeli blockade imposed since then has made it impossible for the vast majority of its 2.3 million residents to leave the territory, where poverty and unemployment are rife.
Source: TRT World