Israeli ground forces attacked Hamas militants and infrastructure on Tuesday in the northern Gaza Strip, from where some 800,000 Palestinians fled in three weeks of hostilities, while several UN agencies warned of the "devastating" situation in the Palestinian enclave. , which for Unicef became a "cemetery for thousands of boys and girls." Jonathan Conricus, an Israeli Army spokesman, said Tuesday that ground operations in Gaza, which began days ago, were focused on the north of the territory, including Gaza City, which he described as "the center of gravity of Hamas." . "But we also continue to attack in other parts of Gaza. We are going after their commanders. We attack their infrastructure, and whenever there is an important target related to Hamas, we attack it," he said. Hamas, Gaza media and witnesses yesterday reported Israeli military incursions into the north and east of Gaza City, which before the hostilities had 650,000 inhabitants. The Army released a video this Tuesday in which soldiers are seen walking through an open field while bursts of gunfire resonate, before taking positions in the ruins of a severely damaged building. Conricus said that some 800,000 Palestinians followed orders from the Israeli army to flee the northern part of the Strip to the south. However, tens of miles of people remain in and around Gaza City, and casualties are expected to rise on both sides as the battle advances into densely populated neighborhoods. The Israeli military said it had struck about 300 militant targets over the past day and that troops had fought several battles with Palestinian militants armed with anti-tank missiles and machine guns.