"This night was the most terrible of all nights ... against the backdrop of the major IDF (Israel Defense Forces) operation in the Strip," the Hostages and Missing Families Forum said in a statement.

It said that the hostages being held by Hamas were being subjected to the same heavy bombardment as Palestinian residents and that their families were racked with "anxiety, frustration" that Israel's long-awaited ground invasion will put them in more danger.

Israel has been bombarding the Gaza Strip, which Palestinian militant group Hamas controls, since Hamas waged a deadly Oct. 7 assault that targeted army outposts and civilian communities in the area and killed 1,400 people, mostly civilians.

Hamas took more than 200 hostages back into Gaza during its raids. It has so far released four and said on Thursday that Israeli bombing had killed another 50 - a claim Reuters could not verify.

Israel's air strikes and artillery fire have demolished large swathes of Gaza and killed more than 7,000 people in the last three weeks, Palestinian health officials say, including some 3,000 children.

Israel said on Saturday that it stepped up ground operations inside Gaza overnight, during internet and power blackouts in the Strip, and that forces were still fighting in the area, without elaborating.

The Hostages and Missing Families Forum criticized Israel's cabinet for not meeting those whose loved ones are still held while Israel presses its assault.

"The families are worried about the fate of their loved ones and are waiting for an explanation. Every minute feels like an eternity," it said.

Israel said on Wednesday that more than half the hostages held by Hamas have foreign passports from 25 different countries. Many were believed to have had dual Israeli nationality.

The hostages are believed to be hidden in the Gaza Strip, possibly in a warren of tunnels Hamas has built there.