GAZA CITY — As international calls for a cease-fire ramped up, the Israeli military warned residents of northern Gaza to evacuate "for their own safety" late Saturday night.
In a statement, the Israeli military said it would send messages to northern Gaza residents overnight to leave their homes as Israel planned to hit the area with heavy force in the next 24 hours, according to Brig. Gen. Motti Almoz, chief military spokesman.
"We are going to attack there with great force in the next 24 hours due to a very large concentration of Hamas efforts in that area," he said.
In the Gaza Strip, 15 people were killed in an Israeli airstrike near a mosque as residents were ending evening prayers, said Ashraf al-Qidra, spokesman for the Palestinian Ministry of Health. The strike marks the single deadliest airstrike in the five-day offensive that has left 135 dead and another 920 injured, according to al-Qidra.
Hamas continued to fire rockets and mortars across its borders at Israel, promising to bombard Tel Aviv with rockets starting at 9 p.m. Saturday night in the hopes of overwhelming the U.S.-funded missile defense system known as "Iron Dome."
Shortly after 9, several defiant Tel Aviv residents sang "We are believers, children of believers, but there is no one to rely on but God" as they watched the defense system destroy a rocket.
Late Saturday, the Israeli military also responded with artillery fire toward the source of two rockets fired from Lebanon that it said caused no injuries or damage.
The developments come as the U.N. Security Council in New York on Saturday called for a cease-fire and the resumption of negotiations between Israeli and Palestinian officials in its first response to the conflict. A statement approved by all 15 members of the council expressed "serious concern regarding the crisis related to Gaza and the protection and welfare of civilians on both sides."
Earlier Saturday, two disabled women were killed when an Israeli airstrike hit a home for disabled people in Beit Lahiya in northern Gaza, al-Qidra said. In southern Gaza, bombs pounded the Islamic National Bank headquarters in Khan Younis, while in Gaza City, three Palestinian fighters were killed. Four were killed at the Martyr Anwar Aziz Square in the Jabaliya refugee camp in northern Gaza.
The Israeli military released an aerial photo of the al-Farouq mosque it said it hit in northern Gaza on Saturday morning, claiming Hamas hid rockets in it right next to another religious site and civilian homes.
"Hamas terrorists systematically exploit and choose to put Palestinians in Gaza in harm's way and continue to locate their positions among civilian areas and mosques, proving once more their disregard for human life and holy sites," said Lt. Col. Peter Lerner, an Israeli military spokesman.
Hamas said Israel hit two mosques in its operation Saturday morning. The competing claims could not be immediately reconciled, but the militant group said it hopes the attack galvanizes support in the Muslim world.
"The bombing of two mosques in Gaza overnight shows how barbaric this enemy is and how much is it hostile to Islam," said Husam Badran, a Hamas spokesman in Doha, Qatar. "This terrorism gives us the right to broaden our response to deter this occupier."
Meanwhile, British Foreign Secretary William Hague called for an "urgent, concerted international action to secure a cease-fire," adding he would be discussing the matter with American, French and German counterparts Monday.
Despite such pressures, Israel has amassed ground troops along the Gaza border and Israeli officials say they will continue the offensive until Hamas and its affiliates stop firing rockets at Israel.
On Saturday, Israeli Defense Minister Moshe Yaalon readied his country for several more days of fighting.
"We have accumulated achievements as far as the price Hamas is paying and we are continuing to destroy significant targets of it and other terror organizations," Yaalon said after a meeting with top security officials. "We will continue to punish it until quiet and security returns to southern Israel and the rest of the country."
Hamas has fired more than 600 rockets in the past week, officials with the militant group said.
In the West Bank on Saturday, one rocket fired from Gaza landed in the Palestinian town of Bethlehem, the traditional place of Jesus' birth, and another in Hebron, where Hamas has a stronghold.
Because Palestinian cities do not have air raid sirens, Hebron residents were reportedly monitoring the sirens of the nearby settlement of Kiryat Arba in order to be alerted to incoming rockets.
Israel has reported no casualties as the Iron Dome has intercepted more than 130 Palestinian rockets.
The Israeli operation, which follows the murders of three Israeli teenagers in the West Bank and the killing of a Palestinian teenager last month, appears more aggressive than the last outbreak of hostilities in November 2012, when an estimated 133 Palestinians were killed.
In Gaza, residents expressed fear over the strikes that have paralyzed life on the Strip.
"It's been days of suffering for the injured and the psychological trauma will linger on," said Mohamed Agwa, 33, of Alborayg in central Gaza. "I heard the screams of children and parents trying to console them while they themselves are terrified and not knowing what was still coming. My heart breaks but that doesn't do any good for those suffering. I feel hopeless."
Anger also appeared to be growing in the region, mainly at the lack of international response to the conflict.
"This morning I am tired, and my anger is threatening to choke me because of so many deaths," said Rawan Alagramy, 55, of Bet Lahiya. "I can't sleep."
"The people of Gaza and the West Bank have as much right as the rest to peace and justice, but the world is silent."
Contributing: Michele Chabin in Jerusalem; The Associated Press