The United Nations says it has been told by the Israeli military that Palestinians and others in the northern Gaza Strip should evacuate to the region's southern areas within 24 hours.

UN spokesperson Stephane Dujarric said the notification was delivered to a UN office in Gaza on Thursday.

According to Dujarric, there are about 1.1 million people in northern Gaza, including Palestinians, UN officials and people taking shelter in UN facilities.

US media outlet Bloomberg reported that the notification indicates the Israeli military may soon start a ground operation in retaliation for an attack by the Palestinian militant group Hamas.

Dujarric said it is "impossible for such a movement to take place without devastating humanitarian consequences." He stated that the UN calls for the order to be rescinded.

Meanwhile, the Israeli military issued a statement on Friday morning, warning all civilians in Gaza to evacuate to the southern region of the Hamas-controlled Gaza Strip. The statement also cautioned people against approaching the border fence with Israel.

It added that the Israeli military will continue a large-scale operation in Gaza City for the next few days, while continuing to make efforts not to harm civilians.