Two Palestinians have been killed in Israeli air strikes in the Gaza Strip, medics say, while an Israeli has been hurt by a rocket fired from there.
A militant was targeted as he launched rockets from northern Gaza overnight. Another man later died near Jabaliya.
An explosion also killed a six-year-old boy in Khan Younis on Saturday. Medics blamed an Israeli air strike, but the Israeli military denied responsibility.
Meanwhile, more than 20 rockets have been fired into southern Israel.
An Israeli man was moderately wounded on Saturday morning when a Qassam rocket hit the roof a factory in the Sderot industrial zone.
The Israeli military's chief of staff, Lt Gen Benny Gantz, has convened "an urgent meeting" to discuss ways of dealing with the rocket- and mortar-fire, which has continued despite efforts this week to agree a ceasefire.
Overnight, the Israel Air Force struck two targets in the Gaza Strip, including the militant preparing to launch rockets. About 20 people, some of them civilians, were wounded.
A man was later killed east of Jabaliya, also in the north, medics said.
Officials from the Hamas militant group, which governs Gaza, said another Israeli air strike killed a six-year-old boy at a football pitch near the southern town of Khan Younis, and wounded two other people.
They also said a baby was wounded in a separate attack in Rafah.
An Israeli military spokeswoman said an initial examination showed that it was not involved in the death of the boy. She suggested the cause could have been a misfired Palestinian rocket.
She had no immediate comment on the report about the baby.
The BBC's Jon Donnison in Ramallah reports that the ceasefire announced on Wednesday never really took root.
Hamas seems to have refrained from firing rockets itself for the last three days but smaller militant groups have continued to do so, he says.
Although neither Hamas nor Israel's leaders say they want an escalation, there is always a fear the fighting could get out of control, our correspondent adds.
It is more than three years since Israel's last major offensive in Gaza, in which some 1,400 Palestinians were killed, as well 13 Israelis.