At least four people have been reported killed in a bomb strike on a rehabilitation centre for the disabled in Gaza, medical sources say, as the toll from Israel's bombardment of the Palestinian territory reaches 151.

Three patients and a nurse were killed in the explosion on Saturday in Jabaliya, the sources told Al Jazeera. They were among a dozen people killed in overnight raids, as Israel's campaign entered its fifth day.

Video footage of the aftermath of the attack, obtained by the Reuters news agency, showed victims being taken to hospital for injuries including severe burns.

The AFP news agency also reported on Saturday that two people had been killed in an explosion at a charitable association for the disabled in Beit Lahiya, three deaths in the eastern Tufah area of Gaza City, and three others killed in western Gaza City.

A mosque in al-Nusarirat, central Gaza, was also destroyed in the overnight raids.

More than 950 people have been injured since Israel began its campaign on Tuesday.

Al Jazeera's Stefanie Dekker, reporting from Al-Shifa hospital in Gaza City, said medical facilities in the territory were overwhelmed.

"Most of the casualties we are seeing here are, overwhelmingly, civilians. It really is a horrendous scene," she said. People are absolutely terrified. The hospitals are having issues with the lack of materials to deal with the people coming in."

Israel is adamant it will continue its campaign, which is says is to stop Hamas missile attacks on Israel.

Fighters in Gaza fired fired rockets at Tel Aviv late on Saturday, the Israeli army said, with media reporting that four were intercepted by Israel's Iron Dome missile defence system.

Benjamin Netanyahu, Israeli prime minister, said late on Friday that he would continue the military campaign until he achieved his goal.

"No international pressure will prevent us acting with all our force against a terror organisation that is calling for our destruction. We will continue to forcefully attack anyone who is trying to hurt us," he said on Friday.

"No terrorist target in Gaza is immune."

Israel said on Saturday that 680 rockets had been fired from Gaza into Israel since Tuesday, injuring nine Israelis.

The army said that they struck a total of 1,160 targets since the beginning of their operation.

Al Jazeera's Bernard Smith, reporting from Jerusalem, said Netanyahu has a lot of support domestically for the offensive in Gaza as Israelis feared the intent Hamas has against them, and Israel's major international allies have not criticised their actions.

"Some sort of natural mediator is what is missing," he said, "In 2012, Egypt, led by then-President Mohamed Morsi, brokered a ceasefire".