Israel has ordered new evacuations in the southern Gaza city of Rafah as it prepares to expand its operation, saying it is also moving into an area in northern Gaza where Hamas has regrouped.

Fighting is escalating across the enclave with heavy clashes between Israeli troops and Palestinian militants on the outskirts of Rafah, leaving crucial nearby aid crossings inaccessible and forcing more than 110,000 people to flee north.

Israel’s move into Rafah has so far been short of the full-scale invasion that it has planned.

The United Nations and other agencies have warned for weeks that an Israeli assault on Rafah, which borders Egypt near the main aid entry points, would cripple humanitarian operations and cause a disastrous surge in civilian casualties.

More than 1.4 million Palestinians — half of Gaza’s population — have been sheltering in Rafah, most after fleeing Israel’s offensives elsewhere.

Israeli army spokesman Avichay Adraee told Palestinians in the cities of Jabaliya and Beit Lahiya and surrounding areas to leave their homes and head to shelters in the west of Gaza City, warning that people were in “a dangerous combat zone” and that Israel was going to strike with “great force”.

Heavy fighting is under way in northern Gaza, where Hamas appeared to have regrouped in an area where Israel has already launched punishing assaults.

Battles erupted this week in the Zeitoun area on the outskirts of Gaza City. Northern Gaza was the first target of the ground offensive, and Israel said late last year that it had mostly dismantled Hamas in the area.

At least 19 people, including eight women and eight children, were killed overnight in central Gaza in three strikes that hit the towns of Zawaida, Maghazi and Deir al Balah, according to Al Aqsa Martyrs Hospital in Deir al Balah and an Associated Press journalist.

Israel’s bombardment and ground offensives in Gaza have killed more than 34,800 Palestinians, mostly women and children, according to the Gaza Health Ministry, which does not distinguish between civilians and combatants in its figures.

Much of Gaza has been destroyed and 80% of its population have been driven from their homes.