[Source: Reuters]

Israeli military strikes across the Palestinian Gaza Strip killed at least 61 people in the space of 48 hours, medics said on Saturday, as Israeli forces battled Hamas-led militants in the territory.

Eleven months into the war, numerous rounds of diplomacy have so far failed to clinch a ceasefire deal to end the conflict and bring the release of Israeli and foreign hostages held in Gaza.

Airstrikes on two former schools that were housing displaced people, one in Gaza City and one in Jabalia, killed at least 12 people, Palestinian medics said.

The Israeli military said the strikes targeted Hamas gunmen who were operating in the compound. Five more people were killed in a strike on a house in Gaza City, Palestinian medics said, with a total of 28 people killed on Saturday.

The armed wings of the Hamas, Islamic Jihad and Fatah groups said they had fought Israeli troops across Gaza with anti-tank rockets and mortar bombs, and in some incidents detonated bombs to target tanks and other army vehicles.

The two warring sides continued to blame one another for the failure of mediators, including Qatar, Egypt and the United States, to broker a ceasefire. The U.S. is preparing to present a new proposal, but the prospects of a breakthrough appear slim as gaps between the sides remain wide.

CIA Director William Burns, the chief U.S. negotiator, told an event in London that a more detailed proposal would be made in the coming days.

Tens of thousands of Israelis joined protests in Tel Aviv and other cities, demanding Prime Minister Benjamin Netanyahu and his government make a deal under which the remaining 101 hostages would be released.

The killing of six hostages last week triggered an outpouring of anger and grief that led to mass protests. The hostages had been shot in the head by Hamas, Israel said, not long before their bodies were found by troops in a Gaza tunnel last Saturday.