GAZA - At least 21 Palestinians were killed and 64 were injured in the continuing Israeli airstrikes on the Gaza Strip, said the Palestinian Health Ministry in Gaza on Wednesday.

Ashraf Al-Qedra, the ministry's spokesman in Gaza, said in a press statement sent to reporters that 21 Palestinians were killed, including 12 civilians, and 64 others were injured by the shrapnel of the Israeli missiles.

The Gaza-based joint chamber of military operations of Palestinian factions claimed firing a barrage of rockets to southern and central Israel on Wednesday, in response to the surprising Israeli airstrikes on Tuesday predawn, which killed three senior members of the Palestinian Islamic Jihad (PIJ) movement's armed wing in the Gaza Strip and their wives and children.

"The chamber claims responsibility for launching hundreds of missiles on the enemy's sites, settlements, and targets, and even Tel Aviv, in response to the assassination of the PIJ leaders," the statement said.

The group comprises several armed wings of Palestinian factions, including the Islamic Resistance Movement (Hamas), the PIJ movement, and other minor military factions and groups.

An Israeli army spokesman said in separate press statements on the same day that the Israeli army targeted dozens of military posts, sites, and operatives belonging to the PIJ military infrastructure by missiles.

Israeli Radio reported that more than 300 rockets and projectiles were fired from the Gaza Strip at southern and central Israel, adding that the Israeli army's Iron Dome intercepted most of the rockets and other rockets landed at empty areas.

Meanwhile, Ismail Haniyeh, politburo chief of Gaza-ruling Hamas, received phone calls from United Nations, Egypt, and Qatar on Wednesday mediating between the Palestinian enclave and Israel to end the flaring tension.

During the phone calls, Haniyeh discussed with the mediators the ways to deal with the Israeli aggression against Gaza in the past two days, and "blamed the Israeli occupation for the escalation and repercussions of this aggression."