Since October 6, the Israeli military has been conducting a major land and air offensive in northern Gaza, particularly targeting the city of Jabalia and its adjacent refugee camp.

The military says it is an effort to prevent Hamas militants from regrouping there, while rescuers say that the offensive has already killed thousands of civilians.

"Fifteen people were martyred and more than 20 were injured in this massacre after midnight in a house where displaced people were living in the town of Jabalia," civil defence agency's spokesman Mahmud Bassal told AFP.

The Israeli military, when contacted, said it was looking into the reported strike.

Bassal said those living in the house were members of the Badra, Abu Warda, and Taroush families who had sought refuge there.

Most of Gaza's 2.4 million people have been displaced at least once since the start of the war on October 7 last year.

The dead and injured from the strike in Jabalia were moved to Al-Mamadani hospital, said rescuer Mohammed, who provided only his first name.

"They were pulled out from beneath the rubble of the targeted house," he said.

A relative of some of the victims said that rescuers were still searching for any survivors under the debris.

"The house has turned into a pile of debris," said Jibri Abu Warda, adding that the strike occurred at around 1:00 am (23:00 GMT Tuesday).

- 'They were all civilians' -

He said the explosions shook the area, and the rescuers were able to reach the targeted house only in the morning.

"It was a massacre, with body parts of children and women scattered everywhere. They were sleeping when the house was bombed," Warda said.

"No one knows why they targeted the house, they were all civilians."

The military assault, which began on October 6, has since expanded across the northern areas of the Palestinian territory and last week targeted a major hospital which is now empty of its staff and patients.

On Friday, the Israeli military raided the Kamal Adwan Hospital in Beit Lahia, describing it as "one of the largest" operations targeting militants since the start of the war.

The military said it killed more than 20 militants and detained over 240 others, including the director of the hospital, who it claims, is a suspected Hamas militant.

Rights groups and the World Health Organisation have called for the immediate release of Hossam Abu Safiyeh, whose detention is seen as a blow to the territory's devastated healthcare system.

In a separate Israeli strike on Wednesday that targeted a group of people in the Al-Manara neighbourhood of Khan Yunis in the territory's south, at least four people were killed, the civil defence agency said.

The war in Gaza broke out after Hamas attacked Israel on October 7 last year, which resulted in the deaths of 1,208 people, mostly civilians, according to an AFP tally based on official Israeli figures.

Israel's retaliatory response has so far killed at least 45,553 people in Gaza, the majority civilians, according to the Hamas-run territory's health ministry, figures which the United Nations considers reliable.