The Israeli warplanes pounded two apartment buildings in Gaza City on Monday, killing at least 12 people, including five children, and wounding 45 others.
The death toll is expected to rise further since 18 of the injured are in critical condition, local medical sources said.
The successive air raids targeted Al-Salam and Al-Israa buildings.
Another air raid killed two people Al-Shamaa district, east Gaza City.
Member of the central committee of the Democratic Front for the Liberation of Palestine (DFLP) Zakaria Abu Daqqa was killed in a similar attack in Absan town, to the south of the Strip while another civilian, identified as Mohammad Ashtowi, was killed in an Israeli artillery bombardment on beguine area to the north of the Strip this afternoon.
More than 21 people have been killed and dozens of others wounded since this evening, and some 100 the whole day.
The hospitals in the southern city of Khan Yunus, including Nasser, the European and the Algerian hospitals are battling to accommodate the large numbers of victims. Today's casualties took to over 500 the number of people killed and 3,300 injured in the Israeli military onslaught on Gaza Strip in the last two weeks.