Palestinian deaths from Israeli air strikes and Palestinian rocket launchings from the Gaza Strip into Israel are threatening the truce which each side tacitly agreed to on Monday.
The Israelis say they will abide by the truce if Hamas, in power in Gaza, makes sure it is respected on its side.
A local Islamic Jihad commander was among those killed.
In the southern Gaza Strip in a strike on smuggling tunnels that run under the enclave’s border with Egypt, one man was killed, two others were critically wounded and three others were missing in the tunnels, medical workers said.
This was on top of the at least six who died in the strikes on the northern Gaza Strip, which also wounded others. Israeli authorities say Islamic Jihad fired 19 rockets and mortars into southern Israel on Wednesday night.
This damaged buildings, and, the police said, a baby in a car that was hit was taken to hospital.
The violence disrupted a ceasefire agreed after the deadly attacks on an Israeli bus and motorists last Thursday.