JERUSALEM: Hamas pledged to confront Israeli attacks with "full force" after Israel's military widened its air and ground attacks on the Palestinian enclave, suggesting on Saturday that a long promised ground offensive had begun.

Israel said on Saturday morning its troops, sent in on Friday night, were still in the field, without elaborating. The country had earlier made only brief sorties into Gaza during three weeks of bombardment to root out Hamas, who it said had killed 1,400 Israelis on Oct. 7.

"The forces are still in the field and continuing the war," Rear Admiral Daniel Hagari told a news briefing on Saturday morning.

Gaza was under an almost complete blackout, with internet and phone services cut for more than 12 hours by Saturday morning. Telecoms firms and the Palestinian Red Crescent Society said it was the result of Israeli bombardments.

Hagari said Israel would allow trucks carrying food, water and medicine to enter Gaza on Saturday, indicating that bombing might pause, at least in the area of its border with Egypt where small amounts of aid have been arriving.

The head of the World Health Organisation (WHO), Tedros Adhanom Ghebreyesus, said the blackout was "making it impossible" for ambulances to reach the injured in Gaza.

"Evacuation of patients is not possible under such circumstances, nor to find safe shelter," he said in a post on X, formerly known as Twitter. He said also the WHO was not able to contact its staff and health facilities.

The Palestinian group that rules Gaza said its fighters were clashing with Israeli troops in areas near the border with Israel.

Hagari had said on Friday evening its ground forces were widening their operations along with extensive air strikes on tunnels dug by Hamas and other infrastructure.

"In addition to the attacks carried out in the last few days, ground forces are expanding their operations tonight," he said.

"Overnight, IDF fighter jets struck 150 underground targets in the northern Gaza Strip, including terror tunnels, underground combat spaces and additional underground infrastructure. Furthermore, several Hamas terrorists were killed," the military said.

The armed wing of Hamas, the al-Qassam brigades, said early on Saturday its fighters were clashing with Israeli troops in Gaza's northeastern town of Beit Hanoun and in the central area of Al-Bureij.

"Al-Qassam Brigades and all Palestinian resistance forces are fully prepared to confront the aggression with full force and thwart the incursions," it said.