Gaza’s health ministry said seven people were killed on Wednesday, a day after Israeli strikes on the Palestinian territory left 15 dead.

Four of those killed on Wednesday were fighters with the Popular Front for the Liberation of Palestine, the group said.

A 10-year-old Palestinian girl named Layan Mdoukh was killed in a blast at her home in Gaza City in unclear circumstances.

“There is a very high sense of worrying,” Al Jazeera’s Youmna El Sayed, reporting from Gaza City, said.

“Everything is closed; schools, private and public facilities have shut down, and people have limited going out of their homes.”

Rana Shubair, a Gaza-based writer, said that the Israeli attacks took them “by surprise completely”. “Everybody was asleep; we suddenly work up to huge explosions,” she told Al Jazeera.

“Barrages of rockets are being launched from the Gaza Strip towards southern Israeli towns,” Sayed added. “We also saw the Iron Dome trying to intercept these rockets.”

The hostilities amount to the heaviest fighting between the sides in months.

Israeli officials said more than 400 rockets had been fired as of Wednesday evening. Most, they said, were intercepted or fell in open areas, but Defence Minister Yoav Gallant said about one-quarter had misfired and fallen inside Gaza.

UN Secretary-General Antonio Guterres condemned civilian deaths in Gaza as “unacceptable” and appealed for them to “stop immediately” and for all parties to exercise maximum restraint, deputy UN spokesperson Farhan Haq said on Wednesday.

“Israel must abide by its obligations under international humanitarian law, including the proportional use of force and taking all feasible precautions to spare civilians and civilian objects in the conduct of military operations,” Haq said.

Renewal of hostilities

The initial Israeli air attacks on Tuesday that set off the exchange of fire killed three senior Palestinian Islamic Jihad fighters and at least 10 civilians, most of them women and children.

Israel has come under international criticism for the high civilian toll from those air attacks, which included wives of two of the hardliner commanders, some of their children and a dentist who lived in one of the targeted buildings along with his wife and son.

The Israeli military has said its attacks were focused on Islamic Jihad infrastructure in the coastal enclave.

A state-run Egyptian TV station announced that Egypt, a frequent mediator between the sides, had brokered a ceasefire on Wednesday. Israeli officials confirmed that Egypt was trying to facilitate a ceasefire.

But truce efforts appeared to falter as fighting intensified late in the day, with neither side showing any sign of backing down.

In a prime-time TV address, Israeli Prime Minister Benjamin Netanyahu claimed that Israel dealt a harsh blow to the fighters.

“This round is not over,” he said. “We say to the terrorists and those who send them. We see you everywhere. You can’t hide, and we choose the place and time to strike you.”

Palestinian Islamic Jihad said it would continue firing rockets. Mohamad al-Hindi, an official with the group, said a sticking point in the talks was that the Palestinians wanted an Israeli commitment to stop targeted killing operations, such as the ones that killed three top Islamic Jihad commanders early Tuesday.

In a statement, an umbrella organisation of Palestinian factions in Gaza, including Hamas, said the campaign against Israel – which it dubbed “Avenging the Free” – involved firing hundreds of rockets in retaliation for Israel’s killing of the three Islamic Jihad commanders as well as several civilians.

“The resistance is ready for all options,” the factions said. “If [Israel] persists in its aggression and arrogance, dark days await it.”

Hamas involvement

It remained unclear whether Hamas had joined the fray.

Mosheer al-Masri, a senior member of Hamas, told Al Jazeera that the Palestinian response to Israeli air raids on Gaza was “a reflection of the resistance’s covenant with its people and martyrs.

“Its hand [the resistance’s] is unified,” he said, adding that “the door of reckoning with the Israeli occupation was still wide open.”

Hamas is among the factions of the Joint Room, but they have not announced their individual participation in the rocket fire.

As rockets streaked through the sky, Israeli TV stations showed air defence systems intercepting rockets above the skies of Tel Aviv. In the nearby suburb of Ramat Gan, people lay face-down on the ground as they took cover.

The Israeli military said that for the first time, an air-defense system known as David’s Sling intercepted a rocket.

The system, developed with the US, is meant to intercept medium-range threats and is part of a multilayered air defence that also includes the better-known Iron Dome anti-rocket system. Israeli media said a previous attempt to use the system several years ago had failed.

Israel and Hamas have fought four wars since the group took control of Gaza in 2007.

In past conflicts, rights groups have accused Israel of committing war crimes due to high civilian deaths. Israel has said it does its utmost to avoid civilian casualties and holds hardliner groups responsible because they operate in heavily populated residential areas.