An Israeli airstrike on a tent camp housing displaced families in southern Gaza killed at least 11 Palestinians, including the head of the Hamas-ruled territory's police force, medics said.
Three children and two women were also reported to be among the dead in al-Mawasi, west of Khan Younis town.
The Hamas-run interior ministry condemned what it called the “assassination” of police director general Mahmoud Salah and his aide Hussam Shahwan, who it said had “fulfilled their humanitarian and national duty”.
Israel's military said it was investigating the reports.
The military has declared the sandy strip of land along the coast in al-Mawasi a “humanitarian zone” for Palestinians displaced by the war with Hamas. But she has repeatedly attacked him, accusing Hamas agents of hiding among displaced civilians.
The recent cold and wet weather has worsened conditions in the makeshift camp.
Over the past day, there have also been deadly Israeli airstrikes in a suburb of Gaza City, further north in Jabalia, and in Bureij in central Gaza – from where the Israeli military says rockets were fired into southern Israel at the very start of the new year.