This is a developing story.

(JTA) — As dawn broke in Israel Sunday, the government officially declared war and confirmed that 100 of its citizens were being held captive in Gaza as fighting in the country’s south continued.

The contours of the previous 24 hours of violence following a broad attack by Hamas were still coming into devastating focus. The estimated death toll leapt from 300 to 700 on Sunday, and the names and horrifying stories of those who had been murdered in their homes and communities are beginning to emerge. More than 2,000 people were wounded, and 100 have been taken hostage to Gaza.

Secretary of State Antony Blinken said that the United States has received reports of Americans that have been killed, wounded and taken hostage, which it is trying to verify. Blinked also announced that the United States would provide new military aid to Israel.

In Gaza, more than 350 Palestinians had been killed in Israeli airstrikes as of Sunday afternoon, according to Hamas figures. Israel’s government issued an official declaration of war, enabling it to carry out “significant military activities.”

Some military breakthroughs were announced overnight, including the freeing of dozens hostages who had been held at Kibbutz Beeri, and of hostages held in a home in the city of Ofakim. But Hamas fighters remained in Israel as of Sunday morning, with fighting ongoing in an untold number of communities. One small town said 15 of its residents had been killed.

Schools in Israel were closed and violence against Israelis is spreading beyond the country’s borders. In Egypt, a gunman shot and killed two Israeli tourists, whose bodies are being flown home.

Videos from Israel showed Israeli civilians held hostage, both in Israel and in Gaza, the Palestinian territory that Hamas controls. Some showed parents trying to comfort their small children despite their circumstances. At least one video circulating appeared to show an Israeli child being held captive.

Anguished parents and relatives posted on social media seeking information about loved ones who remain missing. A widely circulating collage showed dozens of young adults who had been attending an outdoor party in the desert near Gaza that was attacked early; many are presumed dead. Relatives of the missing were being asked to provide DNA samples that could be used in identification.

The names of soldiers who had fallen in combat were also starting to emerge, even as what Israeli Prime Minister Benjamin Netanyahu promised would be a “prolonged and powerful campaign” was just getting underway. The commander of a major infantry brigade was killed, as were an undisclosed number of other soldiers.

Meanwhile, fears were roiling that a second front could open in the north, where Hezbollah, which like Hamas is understood to be a proxy of Iran, operates in Lebanon. Amir Tibon, a Haaretz journalist whose own family was rescued late Saturday from their besieged kibbutz by a battalion including his father, a retired general, cautioned on X that Israelis in the north should prepare themselves for conflict. “We were not prepared properly,” he wrote. “Don’t make this mistake.”