Israeli security forces struggled to quell worsening communal violence in its cities as the military stepped up its assault in Gaza against Palestinian militant group Hamas.

Jews and minority Israeli Arabs clashed in several Israeli towns overnight as Prime Minister Benjamin Netanyahu vowed to subdue riots with “a lot of force”.

The worst domestic unrest in years escalated with a soldier beaten in Jaffa, a police officer shot in Lod and another synagogue set on fire, according to Israeli media. Outbreaks of mob violence were reported around the country as large groups of Israeli Arabs and Jewish men defied curfews.

The brawls between Israeli citizens came as the military added tanks and the artillery to its five-day air campaign against Hamas.

The military operation has killed 119 Palestinians, including 50 women and children, according to health officials in Gaza. “We are dealing with a campaign on two fronts — in Gaza [and] in Israel’s cities,” Netanyahu said late on Thursday.

An Israeli military spokesperson told reporters early on Friday that ground troops had moved into Gaza, but he later clarified that none had entered the impoverished territory of 2m.

Israel had positioned additional troops — including two infantry brigades and one armoured — near the Gaza border and called up a further 9,000 reservists on Thursday.

The troop movement raised speculation that Israel was planning its first invasion of Gaza since its 2014 war with Hamas. Israeli military officials have said they are preparing for all scenarios, including a potential ground offensive, but have not yet taken a decision on whether to invade.

So far only 30 of the dead in Gaza have been identified by the Israeli army as Hamas operatives, and Gaza residents described the Israeli bombardment as more intense than at any point during the 2014 war, which killed more than 2,000 Palestinians. The Israeli military said its new strategy, dubbed the “Victory Doctrine”, used a significantly higher tempo and intensity of attacks, across a wider range of targets.

Despite the relentless Israeli bombardment, Hamas continued to fire rockets deep into Israel overnight, directing hundreds more at Tel Aviv, Ashdod and one much further south that landed near an airport close to the Red Sea, where incoming international flights had been rerouted.

The militant group has fired more than 1,500 rockets into Israel since Monday. Nine Israelis, including a soldier and a child, have been killed.

The UN Security Council said it would hold an open session to discuss the issue on Sunday. The US had wanted to hold it on Tuesday to allow space for its diplomatic efforts to bear fruit, a US official said. US State department official Hady Amr has travelled to the region.

The Arab-Israeli conflict has for more than a decade been dominated by fighting between Israeli forces and Palestinian factions in the occupied territories. But the communal violence inside Israel has added a dangerous new dynamic.

Israeli Arabs account for about one-fifth of the Jewish state’s population, carry Israeli passports and vote in the country’s elections. But they say they suffer from institutional and social discrimination and their sympathy for the Palestinian cause has made them a target for rightwing Israeli politicians.

Several thousand Israeli police have been moved from the occupied West Bank to Israeli cities as part of efforts to stem the communal violence.

Speaking in Lod, a mixed-population town near Tel Aviv that has suffered the worst of the Jewish-Arab fighting, Netanyahu vowed that the security services would be given a free hand to put down the domestic riots. “You have the backing, do not be concerned,” he said. “In putting down rioters one needs to use force, a lot of force.”

The prime minister said he was considering approving the use of administrative detentions, commonly used in the occupied West Bank to detain Palestinians for long periods without access to lawyers, and bringing in the army. That raised fears among Arab Israelis that they could face the same harsh measures Israel has used against Palestinians in occupied territories.

“The intelligence that we have says that it could very well be that we will have an upsurge of violence here in the coming days,” Netanyahu said. “Right now we have no greater threat than these disturbances.”

The violence has underscored the religious tensions that triggered the deepening crisis. Weeks of stand-offs have persisted between Palestinians and Israeli riot police at al-Aqsa mosque in Jerusalem.

Israeli police stormed the compound, which is sacred to both religions, at least three times in the past week, using rubber bullets, tear gas and stun grenades. At least 600 Palestinians were injured.

Hamas stepped into the fray on Monday, firing long-range rockets after demanding that Jewish settlers in Israeli-occupied East Jerusalem stop harassing Arab residents who were awaiting eviction orders from Israeli courts. Israel responded with hundreds of air strikes on Gaza.

The Gaza Strip is down to about five hours of electricity a day and will probably run out of fuel by Sunday, according to an Israeli security official, speaking on condition of anonymity. In an attempt to choke off Hamas’s access to resources, Israel has, since 2007, imposed a blockade on the Gaza Strip, described by the Palestinians as a siege.