Israeli ground forces were confronting Hamas fighters across the Gaza Strip, the Israeli military said on Sunday in its clearest indication yet that a planned ground offensive in the enclave’s refugee-crowded south had begun as Israeli bombing killed and wounded dozens of Palestinians.

The Hamas Palestinian militant group said its fighters clashed with Israeli troops about 2 km (1 mile) from the southern city of Khan Younis.

Residents, many of whom had moved there to flee earlier attacks in the Israel-Palestinian conflict, said they could hear tank fire and feared a new Israeli ground offensive was building.

The Israeli military earlier ordered people to evacuate some areas in and near the city, but did not announce any new southern ground assault.

“The IDF (Israel Defence Forces) continues to extend its ground operation against Hamas centres in all of the Gaza Strip,” spokesperson Rear Admiral Daniel Hagari told reporters in Tel Aviv. “The forces are coming face-to-face with terrorists and killing them.”

Early on Monday, Hamas media quoted emergency services as saying an Israeli strike killed three civil emergency workers in Gaza City in the north of the coastal enclave.

SHIPPING ATTACKS Attacks on shipping in the southern Red Sea on Sunday heightened fears of the conflict spreading.

The U.S. Defense Department said three commercial ships were attacked by Yemen’s Iran-allied Houthi movement in international Red Sea waters, and a U.S. destroyer operating in the area shot down three drones as it responded to distress calls.

A Houthi spokesperson said its navy had attacked two Israeli ships in the Red Sea with an armed drone and a missile on Sunday, though an Israeli military spokesman said the two ships had no connection to Israel.

REFUGEE CAMP STRIKE The Jabalia refugee camp in the north of Hamas-ruled Gaza was among the sites reported hit from the air. A Gazan health ministry spokesperson said several people were killed by an Israeli air strike.

Footage obtained by Reuters showed a boy covered in grey dust, sitting weeping amid crumbled cement and rubble from collapsed buildings.

“My father was martyred,” he cried in a hoarse voice. A girl in a pink sweatshirt, also coated with dust, stood between piles of rubble.

Bombardments from war planes and artillery were also concentrated on Khan Younis and Rafah, another city in Gaza’s south, residents said, and hospitals were struggling to cope with the flow of wounded.

Israel’s government spokesperson, Eylon Levy, said the military had struck more than 400 targets over the weekend “including extensive aerial attacks in the Khan Younis area” and had also killed Hamas militants and destroyed their infrastructure in Beit Lahiya in the north.

There was no immediate comment on the reports of specific attacks.

The renewed warfare followed the end on Friday of a seven-day pause in the fighting between Israeli forces and Hamas militants which had allowed an exchange of 105 hostages held by Hamas, most of them Israelis, for 240 Palestinian prisoners.

The latest violence took place despite calls from the United States — Israel’s closest ally — for Israel to limit harm to Palestinian civilians in the new phase of its offensive, focused on the south.

U.S. Vice President Kamala Harris made phone calls to both Israeli President Isaac Herzog and Palestinian Authority President Mahmoud Abbas on Sunday, reiterating Israel’s right to self-defense and U.S. support for a two-state solution that gives Palestinian people the right to self-determination.

Harris “reiterated our concerns with steps that could escalate tensions, including extremist (Israeli) settler violence,” her office said.

More than 15,523 people have been killed, according to Gaza’s health ministry, in nearly two months of warfare that broke out after a Hamas cross-border raid on southern Israel on Oct. 7 in which 1,200 Israelis were killed and around 240 taken hostage. Israel says Hamas continues to hold 136 hostages.

Israel has vowed to annihilate Hamas. The Iranian-backed group is sworn to Israel’s destruction. The initial Hamas attack and the ensuing war amount to the bloodiest episode in the decades-old wider Israel-Palestinian conflict.

GROUND OFFENSIVE FEARED Gaza residents said earlier on Sunday they feared an Israeli ground offensive on the southern areas was imminent. Tanks had cut off the road between Khan Younis and Deir Al-Balah in central Gaza, effectively dividing the Gaza Strip into three.

The Israeli military ordered Palestinians to evacuate several areas in and around Khan Younis. It posted a map highlighting shelters they should go to west of Khan Younis and south toward Rafah, on the border with Egypt.

Many residents started packing but said that areas they had been told to go to were themselves coming under attack.