Among those killed were four women in the southern city of Rafah and eight people near a hospital in Gaza City in the north, the Palestinian Civil Emergency Service said. Others were killed in separate air strikes across the territory, it said.
The Israeli military said it killed eight Palestinian fighters, including a senior Hamas commander, near Al-Ahli Arab Hospital in Gaza City.
The armed wings of Hamas and Islamic Jihad said they were battling Israeli forces in the Zeitoun suburb of Gaza City, and also in Rafah and Khan Younis in the south.
WHO says it has surpassed early targets for polio vaccination
Meanwhile, Israeli forces killed three people, including a 16-year-old Palestinian girl, in the occupied West Bank on Tuesday, the Palestinian Red Crescent said, as a major Israeli operation in the cities of Jenin and Tulkarm continued for a seventh day.
The girl, identified as Lujain Osama Musleh, was killed in the town of Kafr Dan, just outside Jenin, where Israeli troops have been operating for days and where they demolished a house on Tuesday.
The military gave no immediate details of the incident but said it was looking into the report. Two Palestinians were also killed in the city of Tulkarm, the Palestinian health ministry said.
Nevertheless, the World Health Organisation (WHO) said that it was ahead of its targets for polio vaccinations in Gaza on Tuesday, day three of a mass campaign, and had inoculated about a quarter of children under 10.
The campaign, which was hastened by the discovery of the first polio case in a Gazan baby last month, relies on daily eight-hour pauses in fighting between Israel and Hamas militants in specific areas of the besieged enclave.
Diplomatic efforts to secure a permanent ceasefire and release foreign and Israeli prisoners held in Gaza and return many Palestinians jailed by Israel have stalled, however.
Israeli Prime Minister Benjamin Netanyahu said on Monday that Israeli troops would remain in the Philadelphi corridor on the southern edge of Gaza, one of the main sticking points in reaching a deal to end the fighting and return prisoners.
Hamas, which wants an agreement to end the war and see Israeli forces out of all of the Gaza Strip, says such a condition, among some others, would prevent a deal. Netanyahu says war can only end when Hamas is eradicated.
Polio campaign
The United Nations, in collaboration with the local health authorities, embarked on the third day of a complex campaign to vaccinate around 640,000 children in Gaza.
Rik Peeperkorn, WHO representative for the Occupied Palestinian territories, told reporters in Geneva that it had vaccinated more than 161,000 children under 10 in the central area in the first two days of its campaign, compared with a projection of around 150,000.
“Up until now things are going well,” he said. “These humanitarian pauses, up until now they work. We still have 10 days to go.” He said that some children in southern Gaza were thought to be outside the agreed zone for the pauses and that negotiations continued in order to reach them.
Palestinians say a key reason for the return of polio is the collapse of the health system and the destruction of most Gaza hospitals. Israel accuses Hamas of using hospitals for military purposes, which the group denies.
More than 40,819 Palestinians have been killed and 94,291 injured in Israel’s military offensive on Gaza since Oct 7, the Gaza health ministry said on Tuesday.