Israeli air strikes killed 35 Palestinians on Monday, hiking the Gaza death toll to 103 as global efforts to broker a truce to end the worst violence in four years gathered pace.

In the latest bloodshed, an Israeli missile killed a senior Islamic Jihad militant in a strike on a Gaza City tower housing Palestinian and international media, the Israeli army and militants said.

Leading Republican Senator John McCain suggested Sunday that President Barack Obama should send Bill Clinton as a special envoy to try to negotiate peace between Israel and Hamas.

"The United States should obviously be as heavily influential as they can," McCain told CBS television, referring to the bloody conflict that has raged since Wednesday between Israel and the Gaza Strip's Islamist rulers.

French Foreign Minister Laurent Fabius said on Sunday a ceasefire between Israel and Gaza militants was an urgent necessity and France was willing to help broker a truce.

"War is not an option, it is never an option," he told journalists in Tel Aviv. "There are two key words: urgency and ceasefire," he said.

Palestinian President Mahmoud Abbas called on Sunday for Palestinians to stage peaceful demonstrations against Israel's military offensive on Gaza militant groups.

"I call on the Palestinian people to intensify their peaceful demonstrations in the streets against the Israeli aggression in Gaza," he said at a meeting with the Palestinian leadership.

The Israeli government on Sunday admitted it had become the victim of a mass cyber-warfare campaign with millions of attempts to hack state websites since the start of its Gaza offensive four days ago.

Speaking ahead of the weekly cabinet meeting, Israeli Finance Minister Yuval Steinitz said the government was now waging war on "a second front -- of cyberattacks against Israel."

An Israeli official landed in Cairo on Sunday for Egypt-mediated truce talks with Hamas to end the Gaza conflict, Egyptian security officials said.

The official landed in a small plane at 1100 GMT and was quickly escorted away by intelligence personnel, the security officials said.

Israel's Foreign Minister Avigdor Lieberman said on Sunday that Israel would not negotiate a truce with Gaza Strip's Hamas rulers as long as rocket fire continues from the Palestinian enclave.

"The first and absolute condition for a truce is stopping all fire from Gaza," he said before meeting French Foreign Minister Laurent Fabius, adding that all militant factions in Gaza would have to commit to cease rocket fire.

U.S. President Barack Obama Sunday said it was "preferable" for the Gaza crisis to be ended without a "ramping up" of Israeli military action, as fears mounted of a new invasion of the Hamas-run territory.

"Israel has every right to expect that it does not have missiles fired into its territory," Obama said, adding, "if that can be accomplished without a ramping up of military activity in Gaza, that is preferable".

The Gaza-based offices of a Kremlin-funded international Russian TV broadcaster were severely damaged Sunday in an Israeli raid on two buildings housing Palestinian and other media outlets, the station said.

The Israeli army confirmed attacking the Shurouq center in Gaza City in an attempt to interrupt what it said was Hamas "operational communications" from the building.

Israeli President Shimon Peres said in an interview on Sunday he welcomed efforts by his Egyptian counterpart to secure a ceasefire in the Gaza conflict but accused Hamas of rejecting the proposals.

He also said he could forsee a scaling back of the situation and stressed that Israel was taking great pains not to hit civilians in the Gaza Strip.