GAZA CITY (Ma'an) -- Israeli airstrikes on Thursday killed two Hamas militants in the northern Gaza Strip, bringing the Palestinian death toll to 13 in less than 24 hours.

Al-Qassam Brigades members Rami Hamad and Khaled Abu Nasr were killed in an airstrike east of Jabaliya refugee camp. Their bodies were taken to the Kamal Adwan hospital, medics told Ma'an.

Earlier Thursday, Israel killed a senior police official and two al-Qassam Brigade members. Dozens of Palestinians have been wounded, including a girl whose leg was amputated.

A pregnant woman, a 7-year-old boy and an 11-month-old baby are among at least 13 Palestinians killed since Wednesday evening, when Israel launched a military campaign on the Gaza Strip after assassinating al-Qassam brigades leader Ahmad al-Jaabari.

Armed groups have fired a barrage of mortars at Israeli military sites and across the border. A rocket fired from the Gaza Strip on Thursday struck an apartment building in southern Israel, killing three Israelis.

Meanwhile a separate airstrike targeted the Shujaiyya area of Gaza City shortly after a rocket fired from the Gaza Strip killed three Israelis near the Gaza border.

The airstrike injured six Palestinians including three children and a pregnant woman, medics said. They were transferred to Shifa Hospital in Gaza City, they said.

Separately, an airstrike in Beit Lahiya in the northern Gaza Strip injured four Palestinians including a woman. They were transferred to Kamal Adwan hospital for treatment.