Israel has hit the Gaza Strip with air strikes and artillery fire on the seventh day of its offensive as diplomatic efforts to halt the bloodshed intensified.

Aircraft struck three training facilities of Hamas's military wing, the Qassam Brigades, around the coastal territory early on Monday, but caused no casualties, medics and eyewitnesses said.

They also hit buildings in Gaza City, Deir el-Balah in the southern part of the strip, and in the northern town of Jabaliya, injuring an unspecified number of people.

There was shelling reported in Beit Lahiya, in the far north of the strip, where Israel had earlier warned residents of an impending assault.

World powers prepared to meet over the spiralling violence as the Palestinian death toll from the Israeli air campaign hit 172 with another 1,230 people wounded, the emergency services said.

Fearing for their lives, about 17,000 people have taken shelter in installations of the UN agency for Palestinian refugees, UNRWA, the agency said in a statement.

As the death toll rose, the Gaza-based Palestinian Centre for Human Rights said most of the victims were civilians, putting their number at more than 130, among them 35 children and 26 women.

It also said Israel had destroyed 147 homes and badly damaged hundreds of others.

Syria and Lebanon

So far, no Israelis have been killed, although Hamas has fired hundreds of rockets into the country since the fighting began on July 8, an army spokeswoman told AFP late Sunday. Around 160 had been intercepted, she said.

For the first time during the Israeli operation, a rocket fired from Syria hit the Israeli-occupied sector of the Golan heights but landed on empty ground, causing no casualties.

Israel responded with artillery fire at Syrian army positions, the Israeli military said.

Four rockets fired from southern Lebanon struck northern Israel early on Monday, Lebanese security sources said.

No casualties were reported in Israel and the army responded with artillery fire.

Early on Sunday, Israeli naval commandos staged a brief ground assault in northern Gaza on a mission to destroy longer-range rockets, with the army warning residents to leave the area ahead of a major assault on the sector.

Saturday's death toll was the highest yet with 56 people killed, including 18 people who died in a single strike on a house in Gaza City, medics said.

Eight people were killed in air strikes on Sunday and another two died early Monday of injuries received in earlier raids.

Diplomatic efforts

Despite increasing calls for a ceasefire, Israeli Prime Minister Benjamin Netanyahu said the military was hitting Hamas "with growing force", warning there was no end in sight.

"We do not know when this operation will end," he told ministers.

US Secretary of State John Kerry phoned Netanyahu to renew a US offer to help mediate a truce and he "highlighted the US concern about escalating tensions on the ground," a senior State Department official said.

Kerry also said that he was engaged with regional leaders "to help to stop the rocket fire so calm can be restored and civilian casualties prevented".

On the Palestinian side, president Mahmoud Abbas said he would ask UN chief Ban Ki-moon to "put the State of Palestine under the UN international protection system" in order to address the violence in Gaza.

Pope Francis appealed to world leaders for both prayer and diplomacy to halt the bloodshed, while the German and Italian foreign ministers were both poised to head to the region to join truce efforts, their offices said.

With Palestinian civilians bearing the brunt of the violence, clashes erupted in central Paris as thousands of people protested against Israel and in support of Gaza.

Protesters also rallied across Asia to condemn the Israeli offensive, with 3,000 gathering in Sydney and hundreds more in Hong Kong, New Delhi and Jakarta.

Israel has warned that preparations are under way for a possible ground incursion, with Foreign Minister Avigdor Lieberman saying a decision was expected by Sunday.

But Israeli media said that a meeting of Netanyahu's security cabinet ended Sunday night without giving the order for ground operations.