TEL AVIV, Israel — The Israeli military says it has launched a new ground offensive in Gaza, sending troops back into areas they had retreated from during a nearly two-month ceasefire. This comes a day after Israel broke the ceasefire with a punishing series of airstrikes that killed more than 400 people, many of whom were children, and wounded hundreds more.

In a statement, the Israel Defense Forces (IDF) says it launched a “targeted ground operation” in central and southern Gaza.

The IDF said it aims to expand what it calls the “security perimeter” separating Gaza and Israel, and to create a “partial buffer zone” between the north and south of the Gaza Strip. The IDF says it has “taken control and re-established” its presence in the Netzarim corridor, the large strip of land dividing Gaza’s north and south that troops had occupied during the war and retreated from as part of a January ceasefire agreement.

The actions come as Israeli Defense Minister Israel Katz released a video addressed to “Gaza residents.”

In it, Katz said the hostages must be returned and Hamas removed from power, saying that this message was the “final warning.”

“What comes next will be much harsher, and you will bear the full consequences,” Katz said in Hebrew with Arabic subtitles. “Soon, the evacuation of the population from combat zones will resume. If all Israeli hostages are not released and Hamas is not removed from Gaza, Israel will act with force beyond anything you have ever seen.”

Meanwhile, thousands of protesters took to the streets in several cities in Israel Tuesday night and into Wednesday afternoon and evening to protest the resumption of the war. In Tel Aviv, protesters banged drums and carried posters with the faces of Israeli hostages still held in Gaza, calling for a deal to have them all released immediately. “If there’s no deal, we will burn the country down,” one group chanted.

Thousands more marched toward Israeli Prime Minister Benjamin Netanyahu’s residence in Jerusalem, waving Israeli flags and carrying a banner calling for new elections, and accusing the Israeli government of working against its people.

Polls show a majority of Israelis are against the end of the ceasefire and want negotiations to continue. Many feel this return to war is a huge betrayal, and that Netanyahu and his government are forsaking the remaining hostages, leaving them to die in Gaza. Israel says 24 hostages are still being held alive there and that Hamas is also holding the bodies of 35 hostages.

Israel said Tuesday’s airstrikes targeted mid-level leaders of Hamas. After the barrage, Hamas said five of its leaders were killed. Today, the Gaza Ministry of Health – which does not distinguish between civilians and combatants – said 436 people were killed in the airstrikes. Of those, 183 were children, 94 were women, and 34 were elderly. Men accounted for 125 of the deaths.

Itay Stern contributed to this report from Tel Aviv, Yanal Jabarin from Jerusalem, and Ahmed Abuhamda from Cairo.