At least 12 Palestinians were killed and several more injured across the Gaza Strip on Sunday in Israeli airstrikes that the military said were carried out in response to ceasefire violations by Hamas.

The Gaza civil defence agency said five people were killed and several others hurt when an airstrike targeted a tent sheltering displaced people in the northern city of Jabaliya.

According to the agency, which operates as a rescue force under Hamas authorities, five more people were killed and several injured in a separate early morning strike in the southern city of Khan Younis. It said one more person was killed after Israeli shelling in Gaza City, while one person was killed by Israeli gunfire in Beit Lahia.

Hazem Qassem, a Hamas spokesperson in Gaza, accused Israel of committing a new “massacre” against displaced Palestinians, calling it a serious breach of the ceasefire days before the first meeting of Donald Trump’s Board of Peace.

Despite a US-brokered truce that entered its second phase last month, violence has continued in the Palestinian territory, with Israel and Hamas accusing each other of violating the agreement.

Al-Shifa and Nasser hospitals confirmed they had received the bodies of at least seven people.

“Israel doesn’t understand ceasefires or truces,” Osama Abu Askar, who lost his nephew in the Jabaliya attack, told Agence France-Presse. He said the people killed there were hit as they slept.

“We’ve been living under a truce for months and they’ve still targeted us. Israel operates on this principle – saying one thing and doing another,” Askar added.

Dozens of relatives and mourners gathered at Nasser hospital where the bodies of some of those killed were laid out in white shrouds. Men and women stood in prayer before the funeral, facing the corpses in the hospital compound.

A military official said Israeli forces attacked in response to Hamas violations of the ceasefire agreement. Under the terms of the agreement, which took effect on 10 October, Israeli troops withdrew to positions behind a so-called “yellow line”, although they remain in control of more than half the Palestinian territory.

“The violation included an identification of several armed terrorists who took cover under debris east of the yellow line and adjacent to IDF troops, likely after exiting underground infrastructure in the area,” the official said.

“Crossing the yellow line in the vicinity of IDF troops, while armed, is an explicit ceasefire violation and demonstrates how Hamas systematically violates the ceasefire agreement with intent to harm the troops.”

Israel has unilaterally moved the yellow line deeper into Gaza even though Israeli withdrawals are part of the ceasefire deal, and Hamas has so far rejected demands to lay down its weapons, also envisaged in the plan. Israel has said it will have to force Hamas to disarm if it does not do so.

Gaza’s health ministry says at least 601 people have been killed since the truce began. The Israeli military says at least four of its soldiers have been killed in the same period.

Agence France-Presse and Reuters contributed to this report