From Sara Sidner, Arwa Damon and Chelsea J. Carter
GAZA CITY (CNN) -- Warplanes, drones and rockets criss-crossed the sky over Gaza for the sixth day Monday as Israel pressed its air offensive against Gaza militants. Hamas leader Khaled Meshaal vowed continued resistance against what he called a "criminal enemy."
"We do not want escalation nor do we call for a ground war," he told reporters at a news conference. "But we are not afraid of it nor will we back down."
In Israel, air raid sirens wailed throughout the day and troops shepherded residents into bomb shelters as rockets arced overhead. In Gaza City, rockets streaked away toward Israel as smoke and fire poured from buildings struck by Israeli warplanes or drones. Most businesses were closed, the streets largely empty.
At least two people died Monday afternoon in a strike on a Gaza City office building used by some media outlets, according to Palestinian sources. Ramez Harb, information leader of the military media office of Palestinian Islamic Jihad, died in the attack, the sources said. Among the wounded were two children, the sources said.
Amid the continued violence, diplomatic efforts persisted. U.N. Secretary-General Ban Ki-Moon arrived in Cairo Monday night to see what he could do to encourage truce talks. His arrival comes hours after Egypt's intelligence chief gave an Israeli delegation a letter from Hamas, outlining its conditions for a cease-fire.
However, U.S. President Barack Obama and Israeli President Shimon Peres said the first step toward ending hostilities is for militants to halt rocket attacks on Israel.
"They can stop any suffering in one second," Peres said. "Stop shooting and that's it."
Palestinian health officials said 100 people have died -- 24 of them on Monday -- and 860 have been wounded in Gaza since Israel began its offensive in response to what Israel characterized as incessant rocket attacks by militants. Israeli officials say three people have died and 68 have been wounded in Israel as the result of rocket fire from Gaza.
Militants in Gaza have fired nearly 1,000 rockets at Israel since the conflict began, the Israel Defense Forces said Monday. Roughly 570 have struck Israel and another 307 have been intercepted by Israel's "Iron Dome" defense system, the IDF said. The rest have landed inside the Palestinian territory, the IDF said.
On Monday, militants fired several rockets toward Eshkol in southern Israel. One hit a school that has been closed since the conflict began, the IDF said. Several more rockets fired at Ashkelon -- which has been repeatedly targeted by militants in recent days -- were intercepted by Israel's missile defense system, it said.
Israel carried out 80 strikes on Monday, raising to more than 1,300 the number of sites targeted since it began its bombing campaign on Wednesday, according to the IDF.
The IDF has struck government buildings, police stations and the homes of Hamas officials as well as rocket-launching sites and suspected storage facilities.
Among other targets hit Monday, Israeli forces struck a Gaza City stadium where the IDF said Hamas militants launched rockets toward Israel three days ago. The IDF also hit a building used by media outlets that it first struck on Sunday.
Monday's strike targeted four senior Islamic Jihad members who it said were hiding in the building, including the information chief, the Israeli military said.
The military described the others as key figures in military training, attack planning, long-range rocket operations and arms manufacturing within the organization.
Israeli forces, who targeted the same building on Sunday, said on Twitter that the officials were using reporters as human shields.
"We targeted only the 2nd floor, which is where the senior terrorists were," the IDF said on Twitter. "The rest of the building was unharmed. Direct hit confirmed."
Despite the violence, a general in Egyptian intelligence involved in talks to broker a cease-fire expressed optimism Monday that a deal to stop hostilities could be reached.
The general told CNN that Hamas gave Israel its conditions for a cease-fire through an intermediary, intelligence chief Mohamed Shehata.
"We are optimistic about the negotiations so far," the general said.
No details of the conditions were immediately available, nor was there any immediate confirmation of the letter from Israel.
Earlier, senior Palestinian negotiator Nabil Shaath said Hamas is demanding that Israel stop the airstrikes and end its long blockade of Gaza.
Hamas wants Israel to stop targeting the leadership of Palestinian factions and to expand the waters Palestinian fishermen are allowed to trawl from three miles offshore to 30 miles, said Shaath, who is also a Fatah leader.
"The attempt is to reach a real stable situation. That's why they are asking for commitment on Israeli typical aggression and periodic incursions and constant shooting and firing at the fishermen in the sea," he said.
The territory has been under a crippling economic embargo since Hamas won control of the territory from the Fatah-led Palestinian Authority, which controls the West Bank.
Hamas, a militant fundamentalist Islamic organization, took political control of the Palestinian territory in 2007 after a landslide election. The United States, Israel and the European Union say it is a terrorist group.
Israel, meanwhile, has demanded an end to the rocket attacks.
In a news conference Monday afternoon, Meshaal sounded defiant, saying the morale of Hamas fighters is high and warning Israeli Prime Minister Benjamin Netanyahu that escalating the conflict with a ground invasion would "not be a picnic."
"The goals of the enemy have failed," said Meshaal, who added that he plans to visit Gaza soon.
In addition to Moon and the special Israeli delegation that traveled to Egypt on Monday, a steady stream of Arab League, U.N. and European diplomats were arriving in the region to promote a cease-fire.
Arab League Secretary-General Nabil el-Araby and 16 foreign ministers from the league's member states were to arrive in Gaza on Tuesday for talks, a spokesman for the organization said. Turkish Foreign Minister Ahmet Davutoglu is expected to join the delegation, a ministry spokesman said Monday.
Palestinian Authority President Mahmoud Abbas, meanwhile, will hold talks in the West Bank with the U.N. secretary-general during his visit to the region, said Saeb Erakat, a member of the PLO's executive committee and an Abbas ally.
"This must stop," Ban said late Sunday. He called on both sides to cooperate with Egyptian-led effort to broker a cease-fire.
"I am heading to the region to appeal personally for ending the violence and contribute to ongoing efforts to that end," he said.
Ban joins a growing chorus of Western and Arab diplomats calling for end to the crisis that has raised fears of a repeat of Israel's 2008 invasion of Gaza following a similar spate of rocket attacks. At least 1,400 people were killed in that conflict.
Ban's call for a truce came on the heels of the single deadliest attack -- an Israeli airstrike that left a family of 10 dead within the building's broken concrete and mangled metal.
Neighbors and family members used a ditch digger, shovels and their hands to dig through the debris of a two-story house blown apart by the Israeli airstrike.
A ditch digger was used to lift a giant slab of concrete. Underneath, the bodies of two small children were discovered.
Nearby, men dug through concrete blocks to find a missing woman.
"She's my uncle's wife," a young man shouted as he tried to get to a debris pile where the woman was believed buried. "She lived here."
A short time later, the body of the elderly woman was uncovered.
On Twitter, the al Qassam Brigades -- Hamas' military arm -- called it a "massacre committed by Israeli occupation."
The Israeli airstrike targeted Yehya Bayaa, "a senior Hamas member," said Lt. Col. Avital Leibovich, the Israel Defense Forces' chief spokeswoman. The IDF alleges Bayaa is one of the leaders of a Hamas rocket-launching unit.
"When I say a senior Hamas member, I mean members that have Israeli blood on their hands -- members of Hamas that planned either the abduction of soldiers or are very much involved in targeting Israelis," Leibovich said.
The house was Bayaa's home and suspected command center, according to Leibovich. She said the Israeli military was examining video of the strike to look for signs of secondary explosions, an indication that there were explosives inside. Initially, the IDF reported it killed Bayaa in the attack. But late Sunday, Leibovich said she did not know for sure whether Bayaa had been killed.
Rockets flew overhead as mourners gathered Monday at the al-Isra mosque for the funeral of some of the family members killed, CNN's Ben Wedeman reported. A short time later, the sound of the firing of more rockets could be heard.
Hundreds turned out for the funeral, where some chanted, "revenge, revenge."
The fighting has put new strains on Israel's relationship with Egypt, which is attempting to broker a cease-fire. The Muslim Brotherhood-led government that took power in June has pledged to maintain Egypt's peace treaty with Israel -- the cornerstone of what peace has been achieved in the turbulent region -- but sympathy for the Palestinians runs deep among Egyptians.
On Monday, Peres praised Egyptian President Mohamed Morsy's efforts to find a solution, saying he is playing a "constructive role."
The United States and several European countries have put the brunt of the blame for the current crisis on Hamas, saying Israel has a right to self-defense, while Arab and Muslim nations have accused Israel of being the aggressor.
Catherine Ashton, the EU's foreign policy chief, repeated on Monday her previous calls for a long-term solution in Gaza.
"I'm very concerned about the loss of life, but I've also been saying consistently for a long time that we need to find a long-term solution to Gaza," she said. "I've been there three times and we have to find a way to prevent the kind of violent rocket attacks that we've seen, and also to bring some security and peace to the people of that region."
CNN's Sara Sidner and Arwa Damon reported from Gaza City; CNN's Chelsea J. Carter reported from Atlanta; CNN's Ben Wedeman, Fred Pleitgen, Amir Ahmed, Jessica Yellin and Mohamed Fadel Fahmy contributed to this report.
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