"Isarel bombards Gaza Strip"

Israel has destroyed the headquarters of the Hamas prime minister and blasted a sprawling network of smuggling tunnels in the southern Gaza Strip, broadening a blistering four-day-old offensive against the Islamic militant group even as diplomatic efforts to broker a ceasefire appeared to be gaining steam.

In neighbouring Egypt, President Mohamed Morsi hosted leaders from Hamas and two key allies, Qatar and Turkey, to seek a way to end the fighting.

"There are discussions about the ways to bring a ceasefire soon, but there are no guarantees until now," Morsi said at a news conference on Saturday.

The Egyptian leader said he was working with representatives from Turkey, the Arab world, the US, Russia and western European countries to halt the fighting.

Israel launched the operation on Wednesday in what it said was an effort to end months of rocket fire out of the Hamas-ruled territory. It began the offensive with an unexpected airstrike that killed Hamas's powerful military chief, and since then has relentlessly targeted suspected rocket launchers and storage sites.

Fresh Israeli air strikes on Sunday hit a Gaza City media centre and homes in northern Gaza as the death toll mounted, despite suggestions from Morsi about the ceasefire.

"At least six journalists were wounded, with minor and moderate injuries, when Israeli warplanes hit the al-Quds TV office in the Showa and Housari building in the Rimal neighbourhood of Gaza City," Gaza health ministry spokesman Ashraf al-Qudra told AFP.

Witnesses reported extensive damage to the building and said journalists had been evacuated after an initial strike, which was followed by at least two more on the site.

In the northern strip, Israeli war planes carried out two separate raids on houses that killed two and injured 10 others, Qudra said.

In Gaza City, as the Israeli war planes attacked from above its naval forces opened fire, launching more than a dozen shells towards the shore, an AFP correspondent reported.

In all, 46 Palestinians, including 15 civilians, have been killed and more than 400 civilians wounded, according to medical officials. Three Israeli civilians have been killed and more than 50 wounded.

Israeli military officials expressed satisfaction with their progress on Saturday, claiming they have inflicted heavy damage on Hamas.

"Most of their capabilities have been destroyed," Major General Tal Russo, Israel's southern commander, told reporters. Asked whether Israel was ready to send ground troops into Gaza, he said: "Absolutely."

The White House said President Barack Obama was also in touch with the Egyptian and Turkish leaders. The US has solidly backed Israel so far.

Speaking on Air Force One, Deputy National Security Adviser Ben Rhodes said the White House believed Israel "has the right to defend itself" against attack and that the Israelis will make their own decisions about their "military tactics and operations".

Despite the bruising offensive, Israel has failed to slow the barrages of rockets from Gaza.

The Israeli military said 160 rockets were launched into Israel on Saturday, raising the total number to roughly 500 since this week's fighting began. Eight Israelis, including five civilians, were lightly wounded on Saturday, the army said.

Israel carried out at least 300 airstrikes on Saturday, the military said, and it broadened its array of targets. One air raid flattened the three-storey office building used by Hamas Prime Minister Ismail Haniyeh. He was not inside the building at the time.

In southern Gaza, aircraft went after the tunnels that militants use to smuggle in weapons and other contraband from Egypt. Tunnel operators said the intensity of the bombing was unprecedented, and that massive explosions could be heard kilometres away, both in Gaza and in Egypt.

Air attacks knocked out five electricity transformers, cutting off power to more than 400,000 people in southern Gaza, according to the Gaza electricity distribution company. People switched on backup generators for limited electrical supplies.

Hamas this week unveiled an arsenal of more powerful, longer-range rockets, and for the first time has struck at Israel's two largest cities, Jerusalem and Tel Aviv. Both cities, more than 70km from Gaza, had previously been beyond rocket range.

In a psychological boost for Israel, a new rocket-defence system known as "Iron Dome" knocked down a rocket headed towards Tel Aviv, eliciting cheers from relieved residents huddled in fear after air-raid sirens sounded in the city.