Israel’s military scoured the country’s south for Hamas fighters and guarded breaches in its border fence with tanks on Monday, as it pounded the Gaza Strip from the air and mustered for a campaign its prime minister said would destroy “the military and governing capabilities” of the militant group.

More than two days after Hamas launched its unprecedented incursion from Gaza, the military said the fighting had largely died down for now. The attack caught Israel’s vaunted military and intelligence apparatus completely off guard, bringing heavy battles to its streets for the first time in decades.

Israel formally declared war on Sunday, portending greater fighting ahead, and a possible ground assault into Gaza — a move that in the past has brought intensified casualties. Palestinian militants continued firing barrages of rockets, setting off air raid sirens in Jerusalem and Tel Aviv.

Civilians are already paying a high price. Around 700 people have been killed in Israel — a staggering toll by the scale of its recent conflicts. Nearly 500 have been killed in Gaza, a tiny, impoverished enclave of 2.3 million Palestinians bordering Israel and Egypt. Palestinian militant groups claimed to be holding over 130 captives from the Israeli side.

Israeli Defense Minister Yoav Gallant meanwhile ordered a “complete siege” on Gaza, saying authorities would cut electricity and block the entry of food and fuel. Israel and Egypt have imposed various levels of blockade on Gaza since Hamas seized power from rival Palestinian forces in 2007.

The chief military spokesman, Rear Adm. Daniel Hagari, told reporters Israel has “control” of its border communities. He said there had been some isolated incidents early Monday, but that “at this stage, there is no fighting in the communities.” He added that “there might still be terrorists in the region.”

Israeli tanks and drones, meanwhile, guarded openings in the border fence to prevent more infiltrations, Hagari said, adding that 15 of 24 border communities have been evacuated, with the rest expected to be evacuated in over the next 24 hours.

Earlier, Hamas spokesman Abdel-Latif al-Qanoua told The Associated Press over the phone that the group’s fighters continued to battle outside Gaza and had captured more Israelis as recently as Monday morning.

He said the group aims to free all Palestinian prisoners held by Israel, which in the past has agreed to painful, lopsided exchange deals in which it released large numbers of prisoners for individual captives or even the remains of soldiers.

Meanwhile, Israel hit more than 1,000 targets in Gaza, its military said, including airstrikes that leveled much of the town of Beit Hanoun in the enclave’s northeast corner. Hagari said Hamas was using the town as a staging ground for attacks. There was no immediate word on casualties, and most of the community’s population of tens of thousands likely fled beforehand.

Hagari said the army had called up around 300,000 reservists — a massive mobilization — and that Israel would aim to end Hamas’ rule of Gaza.

“Our task is to make sure that Hamas will no longer have any military capabilities to threaten Israel,” said spokesperson Jonathan Conricus in a video tweeted by Israel’s military. “And in addition to that, we will make sure that Hamas is no longer able to govern the Gaza Strip.”