Jerusalem — Palestinian militants in the Gaza Strip on Sunday intensified a wave of rocket fire into southern Israel, striking towns and cities across the region, killing at least one person and seriously wounding three others in one of the bloodiest rounds of fighting since the 2014 war. At least eight Palestinians, including a pregnant woman and her 14-month-old niece, have also been killed.

Israeli forces struck dozens of targets throughout Gaza, including militant sites that it said were concealed in homes or residential areas. The army also moved armored units toward the Gaza perimeter as the sides headed closer to all-out war.

Moshe Agadi, a 58-year-old Israeli father of four, was struck in the chest by shrapnel in a residential courtyard from one of the 450 rockets fired from Gaza in less than 24 hours. Then a midday barrage hit Ashkelon again, wounding three people, including two seriously who were suffering from "multisystem trauma." The Magen David Adom rescue service said another person was critically wounded when a rocket landed on a car near the Gaza boundary.

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The Israeli military has retaliated with some 260 airstrikes against militant targets in Gaza.

A car hit by a missile fired from Gaza, is seen near the Gaza and Israel border, Sunday, May 5, 2019. Ariel Schalit / AP

The Palestinian Health Ministry had previously said an Israeli strike on Saturday killed a pregnant woman, Falistin Abu Arar, 37, and her niece, Seba Abu Arar, in their east Gaza City home.

However, military spokesman Lt. Col. Jonathan Conricus said Sunday that a detailed review found that a Palestinian rocket had misfired and killed them. He said the Palestinians were "trying to sell a story that isn't true." The conflicting accounts could not immediately be reconciled.

Hospital officials in Gaza confirmed the deaths of two men, ages 28 and 21. Islamic Jihad media outlets said the two were militants. Their deaths raised to nine the number of Palestinians killed in the recent fighting.

The sudden outburst has broken a month-long lull as Egyptian mediators had been trying to negotiate a long-term cease-fire between the two sides, who have fought three wars and several other rounds of conflict over the past decade.

Conricus said Israel's strikes hit a variety of "high-quality" militant sites, that included commanders' homes in which militant activity was observed. He said he had no knowledge of civilians being harmed by Israeli fire.

The military spokesman said Israel was deploying an armored brigade along the Gaza front, with tanks ready for offensive missions as needed. The Israeli military has already struck rocket launchers, tunnel shafts, training sites, storage depots and warehouses of both the territory's Hamas rulers and the smaller, Iranian-backed Islamic Jihad group.

Israeli Prime Minister Benjamin Netanyahu said Hamas was paying a "heavy price" for its rocket attacks against Israel and that it would be held accountable not only for its own militant actions but also for that of the Islamic Jihad, which operates under its jurisdiction in Gaza.

Sirens wailed along the border region overnight and throughout the day warning of incoming attacks. School was canceled in southern Israel and emergency protocol enacted. As the day progressed, rockets were being fired deeper into the Israeli heartland.

In Gaza, large explosions thundered across the blockaded enclave during the night as plumes of smoke rose into the air.

By morning, bulldozers were clearing the streets from rubble and debris strewn on the ground and municipal workers were fixing damaged power lines. Owners of clothing stores that were destroyed in Gaza City's relatively upscale Remal neighborhood squatted across the streets from where their stores had stood, cupping their faces in their hands.

A view shows the remains of a building that was destroyed in Israeli air strikes in Gaza City on May 5, 2019. SUHAIB SALEM / REUTERS

One of the airstrikes hit a six-story commercial and residential building that housed the office of Turkey's official Anadolu news agency.

"We thought the Rimal neighborhood is safe, but it seems there is no safe place in Gaza," said Nidal al-Dali, who lived in the building and lost his home.

Turkish Foreign Minister Mevlut Cavusoglu called it a "new example of Israel's unrestrained aggression."

The Israeli military says its Iron Dome defense system intercepted more than 150 of the projectiles from Gaza, but several still managed to slip through. A rocket scored a direct hit on a residential home in the border town of Sderot.

Jonathan Rieck, director of the emergency room at Barzilai Medical Center in Ashkelon, said they had treated some 80 people, most from shock symptoms, but several with body wounds, including an elderly man who was in critical condition from head injuries. In a first, the hospital itself was also hit by debris from a rocket that was intercepted by an Iron Dome missile. There were no injuries.

Israeli Iron Dome air defense system takes out rockets fired from Gaza, near the Gaza and Israel border, Sunday, May 5, 2019. Ariel Schalit / AP

Israel has vowed to hit back hard against both Hamas and Islamic Jihad, whom it suspects of triggering the current conflagration. But, as in similar previous rounds where it stopped short of a full-fledged war, the timing for a prolonged round of fighting is tricky for Israel.

The country marks Memorial Day and Independence Day this week. The following week it is set to host the Eurovision song contest in which large groups of tourists are expected to arrive for the festive event.

For Gazans, the violence comes ahead of the Muslim holy fasting month of Ramadan that begins Monday.

Hamas, an Islamic group vowed to Israel's destruction, forcefully seized control of Gaza in 2007. It most recently engaged in several days of heavy fighting with Israel in March before Egypt brokered a truce, in which Israel agreed to ease a crippling blockade on Gaza in exchange for a halt in rocket fire.

In recent days, Hamas accused Israel of reneging on its pledges as militants began to fire rockets into Israel. Israel accuses Islamic Jihad of operating behind Hamas' back and instigating the latest round of violence by shooting and wounding two Israeli soldiers Friday. Two Palestinians were shot dead by Israeli forces the same day during the weekly protests along the Israel-Gaza perimeter fence.

Yaakov Amidror, a former Israeli national security adviser, said the violence was being instigated by Islamic Jihad militants in Gaza at the behest of their backers in Iran. Amidror, currently a senior fellow at the Jerusalem Institute for Strategy and Security, said a new war in Gaza would distract Israel and leave Tehran "free to continue what they are doing in Syria."

The resurgence of violence threatened to shatter the shaky understandings recently reached though Egyptian mediators. Militant leaders were in Cairo trying to reach a new cease-fire.

Hamas has hoped that Egyptian mediators could further ease the blockade, which has ravaged Gaza's economy. For over a year, the Islamic group has orchestrated mass demonstrations each week along the Israeli frontier to draw attention to Gaza's plight. More than 200 Palestinians and an Israeli soldier have been killed in the border protests.