The Israeli military has killed at least 39 Palestinians in overnight strikes across the Gaza Strip, medics said, including at least 21 in an attack that set ablaze tents sheltering displaced Palestinian families in a crowded camp.

Residents carried a body wrapped in carpets out of the charred wreckage of the makeshift shelters in al-Mawasi, near the beach west of Khan Younis in southern Gaza, where tens of thousands of people have sheltered for months. Israel calls the area a so-called “safe zone”, but has repeatedly attacked displacement tents in the area.

Mourners said the latest attacks demonstrated that a new declaration from international human rights group Amnesty International that Israel was guilty of genocide in Gaza had come too late.

Gaza medics said the 21 confirmed killed in the Israeli strike there included women and children. Israel claimed the strike targeted senior Hamas members, whom it did not identify.

Later on Thursday, Hussam Abu Safia, director of Kamal Adwan Hospital in Beit Lahiya in the north of the enclave, said a 16-year-old boy who used a wheelchair was killed and several people, including medics, were wounded in a drone attack at the medical facility.

The Health Ministry said three hospitals that are barely operational on the northern edge of the Gaza Strip have come under repeated attack since Israeli forces sent tanks to Beit Lahiya and Beit Hanoon towns and the nearby Jabalia refugee camp in October in a renewed ground assault and siege on northern Gaza.

The siege has exacerbated an already dire humanitarian situation, with famine looming and the healthcare system collapsed.

‘Stop this crazy war’

The strike at al-Mawasi set several large tents ablaze and exploding cooking gas canisters and burning furniture fuelled the fire. The area was strewn with charred clothing, mattresses and other belongings among the twisted frames of burned-out shelters.

“We don’t see anyone from the whole world standing by us or helping us in this situation. Let them stop this crazy war that’s against us. Let them stop the war,” said Abu Kamal al-Assar, a witness at the site.

Al Jazeera’s Tareq Abu Azzoum, reporting from the site of the attack in Khan Younis, said the strike “encapsulates the catastrophic calamity Palestinians are really going through, especially since there are not any places across the Gaza Strip or even shelters that could be safe”.

The attack came on the day Amnesty International released a report saying Israel’s actions in Gaza met the definition of the crime of genocide. Israel strongly rejected that accusation, denouncing Amnesty as a “deplorable and fanatical organisation”. The United States, a key ally, also rejected the Amnesty allegation.

In southern Gaza at a funeral in Khan Younis, where relatives wept over white-shrouded bodies, resident Abu Anas Mustafa called the Amnesty report “a victory for Palestinian diplomacy”, although he said it came late.

“It is the 430th day of the war today, and Israel has been carrying out massacres and a genocide from the first 10 days of the war,” he said.

Israeli strikes on Thursday pounded Gaza City, where medics said an attack, which destroyed a house where an extended family had taken shelter and damaged two nearby homes, killed at least three people.

In Rafah, near the border with Egypt, an Israeli strike killed three Palestinians on Thursday, medics said. Three others were killed in a separate air strike in Shujayea, in eastern Gaza City, they added.

Israel launched its assault on Gaza in October last year, forcing nearly the entire 2.3 million population from their homes. More than 44,500 Palestinians have been killed, with thousands of others feared dead under the rubble.

Basem Naim, an official in Hamas’s political bureau said that international mediators have resumed negotiating with the group and Israel over a potential ceasefire in Gaza, and that he was hopeful a deal was within reach.

Ceasefire negotiations were halted last month when Qatar suspended talks with mediators from Egypt and the United States because of frustration over a lack of progress.

But there has been a “reactivation” of efforts in recent days to end the fighting, release captives from Gaza and free Palestinian prisoners in Israel, according to Naim.