JERUSALEM (CNN) — Eight activists formed a human shield outside a hospital in Gaza Saturday, a doctor said, as Hamas and Israel battled it out with rockets and airstrikes.
Israeli strikes have killed 121 people in Gaza this week, according to the Gaza health ministry. It said 924 others have been injured.
An Israeli airstrike hit a facility housing the disabled, killing two women, the health ministry said Saturday. The Israel Defense Forces said it was looking into that claim.
Gaza militants have fired about 690 rockets and mortars toward Israel, 138 of which the latter intercepted, according to the Israeli military.
As the two sides exchange blows, hospitals hoped to remain open.
In Gaza, activists who formed a human shield are from various countries, including the U.S., Venezuela, Belgium, Britain and Switzerland, said Dr. Basman Al-Ashi, executive director of the Al-Wafa hospital. He said the hospital caters to patients who need 24-hour care, and thus cannot evacuate them.
Medical sources described overcrowded emergency rooms in Gaza and dwindling stocks of medicine, a situation that mirrored Syrian hospitals at the height of its civil war.
Gaza hospitals not directly affected by airstrikes face significant challenges, including rolling blackouts and water shortages in some areas because airstrikes have damaged pumping stations.
Though some Israelis have been wounded, none have been killed by the hundreds of rockets fired by Hamas and other militant groups in Gaza. Israel's Iron Dome defense system has intercepted dozens of rockets, helping keep fatalities at bay.
Hostilities between the two sides escalated this month after the killing of three Israeli teenagers and a Palestinian teen. Neither Hamas nor Israel appear to be backing down, prompting fears of a ground invasion by the latter.
Israeli Prime Minister Benjamin Netanyahu left all possibilities open, saying the international community will not influence his actions against Hamas. He reiterated that there is one path to a cease-fire: the cessation of attacks from Gaza.
"We are considering all options and getting ready for every possible scenario," he said. "All the citizens of Israel are aware of my major goal, and this is to bring back the quiet to all Israeli territories. Hamas keeps attacking us, and therefore we are fighting them back."
Israel faced attack from a second front Friday when a rocket launched from Lebanon landed near the northern Israeli town of Metula, which sits right by the border. No damage or injuries have been reported. It was not immediately clear who fired the rocket.
Hezbollah operates in Lebanon and is caught up in other conflicts in the region, which makes starting a war with Israel less likely for the group.
Thousands of rockets were fired from Lebanon into Israel during a war in 2006, but rocket attacks since then have been sporadic.
Nonetheless, Israel responded with artillery that landed in the vicinity of the Lebanese town of Kfar Shouba. No casualties were reported, the Lebanese army said.
Israel calls up reservists
As fears of an Israeli ground assault grew among Gaza residents, Israel revealed it has beefed up its forces by calling about 30,000 reservists to their units.
"We are utilizing that force to enable us to create a substantial force around Gaza, that if it is required, we'll be able to mobilize as soon as possible," Israel Defense Forces spokesman Peter Lerner said.
The Israeli Cabinet has authorized the military to call up 40,000 troops if needed. That is 10,000 more than were called up during Israel's offensive into Gaza in November 2012.
The Israeli military said it hit more than 60 targets in Gaza on Friday night, bringing the total to 1,160 strikes since the beginning of Operation Protective Edge.
Hamas and other militant groups in Gaza are believed to have about 10,000 rockets of varying ranges, according to the Israeli military. Israel has said some 3.5 million residents live in areas within reach of the rockets.
U.S. willing to help broker cease-fire
Hopes for a cease-fire appeared dim even as world leaders called for the two sides to stop the violence.
U.S. President Barack Obama spoke with Netanyahu by phone.
"The United States remains prepared to facilitate a cessation of hostilities, including a return to the November 2012 cease-fire agreement," the White House said in a written statement, referring to the Egyptian-brokered deal that halted the previous Israel-Hamas conflict.
The President also condemned rocket attacks from Gaza and said the United States reaffirmed Israel's right to defend itself.
CNN's Kareem Khadder reported from Jerusalem, and Yousuf Basil reported from Atlanta
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