Two people died in explosions involving car bombs in the Tel Aviv district of Jaffa and in the suburb of Holon.
Three others were killed in two separate homicides in Israel's Arab communities.
All four incidents are linked to organised or criminal violence, according to the police's findings.
A paramedic said emergency services arrived quickly at the scene after a report of an explosion in the city of Holon south of Tel Aviv.
"There we saw that the vehicle was on fire. The driver was lying next to the car."
He was unconscious and seriously injured.
His death was later confirmed in hospital, according to media reports.
In the car explosion in Jaffa, the driver's six-year-old son was in the vehicle with him, according to the news portal Ynet.
The child was injured and taken to hospital.
Investigators are examining suspicion that the act was carried out as revenge for the killing of a teenager last week, it said.
Meanwhile, two people were shot dead in the Israeli Arab town of Kalansuwa.
Police suspect this violence was due to a feud between two families, Ynet reported.
Overnight a 19-year-old was shot dead outside his home in the Arab town of Tayibe.
Authorities suspect criminals are involved in that case.
Israel's government is repeatedly accused of not acting decisively enough against violent crime within Arab society.
Since the start of the year, about 140 people have died as a result of violence within Israel's Arab population, according to media reports.
The Arab minority makes up about 20 per cent of Israel's 10 million inhabitants.
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