Cairo/IBNS: Three sons of Hamas leader Ismail Haniyeh were killed in an Israeli airstrike on Gaza Strip on Wednesday, media reports said.

Haniyeh's three sons - Hazem, Amir and Mohammad - were killed after the car they were driving in was bombed in Gaza's Al-Shati camp, the Hamas group was quoted as saying by Reuters.

Two of Haniyeh's grandchildren were also killed in the attack and a third was wounded, Hamas media said.

"Our demands are clear and specific and we will not make concessions on them. The enemy will be delusional if it thinks that targeting my sons, at the climax of the negotiations and before the movement sends its response, will push Hamas to change its position," Haniyeh told pan-Arab Al Jazeera TV.

"The blood of my sons is not dearer than the blood of our people," said Haniyeh, who is based abroad in the Gulf Arab state of Qatar.

Haniyeh has been the tough-talking face of Hamas' international diplomacy in its war with Israel. His family home in Gaza was destroyed in an Israeli airstrike back in November.

Hamas said on Tuesday it was going through an Israeli ceasefire proposal but that it was "intransigent" and did not meet any of the Palestinian demands.

In the seventh month of a war with Israel that has devastated Gaza, Hamas wants an end to Israeli military operations and a withdrawal from the enclave, and permission for displaced Palestinians to return home.