Israeli aircraft struck the Gaza Strip repeatedly early on Sunday and the army said it had targeted sites used by militants firing rockets into Israel and roads for transporting the makeshift missiles.
Four Palestinians were wounded in at least nine raids, including three policeman and a baby who was hit in the face with shrapnel, medics said.
Key bridges in the northern Gaza Strip were also targeted, cutting roads for thousands of people.
“These routes are used by terrorists to reach the areas from which they launch rockets at Israeli targets,” the army said.
Israeli warplanes also carried out mock raids over Gaza City, shaking homes with deafening sonic booms.
Repeated violence has dimmed hopes for peacemaking that had been kindled by Israel’s withdrawal of troops and settlers from the impoverished Gaza Strip in September after 38 years of occupation.
Militant groups agreed to follow a truce until the end of the year in order to smooth the Gaza pullout, but their commitment to “ensure calm” formally expires at the end of the year.
Palestinian factions have fired rockets at Israel in retaliation for deadly raids against militants that in turn followed a suicide bombing that killed five Israelis on December 5.
Two rockets struck southern Israel on Saturday and the army responded by firing artillery shells toward open fields in northern Gaza. Nobody was hurt in either incident.
A Palestinian militant was also killed in an explosion in a car in the southern Gaza Strip on Saturday which Palestinian officials blamed on Israel.
But the Israeli army denied any involvement in the death of Khaled Abu Sitta, a senior leader of the Abu el-Reesh Brigades, who was killed when his car blew up as he drove at night between the southern Gaza cities of Khan Younis and Rafah.
Palestinian security sources and members of the Abu el-Reesh Brigades said an Israeli missile fired from an unidentified aircraft hit Sitta’s car, killing him and turning the vehicle into a mound of charred and twisted metal.
The Abu el-Reesh Brigades said they would avenge Sitta’s death.
“We do not forget the blood of our martyrs and our reaction will be strong and painful,” said Abu Haron, a spokesman for the group, which is linked to the mainstream Fatah faction of President Mahmoud Abbas.
The Israeli army, which often openly admits to strikes on militants’ cars, denied involvement in the incident.
Palestinian militants have also occasionally been killed when explosives they were transporting detonated prematurely.