Israeli rescue workers and paramedics carry injured woman from the site of bus bombing in Tel Aviv Nov. 21, 2012 / AP
Near the Israel-Gaza border (CNN) -- A bomb exploded on a bus in Tel Aviv as it passed by Israeli army headquarters around noon Wednesday.
The attack, which police said left 18 passengers injured, shook up the Israeli public and threatened to complicate efforts to achieve a cease-fire on the eighth day of violence between Israel and Gaza.
Meanwhile, overnight and into Wednesday, Israeli bombs and artillery turned buildings, tunnels and bridges in Gaza into rubble in 100 strikes confirmed by Israeli authorities. At the same time, Hamas media boasted about their militants' rockets hissing off in the direction of populated areas of southern Israel.
The bus attack left three people hospitalized in serious condition, police spokesman Mickey Rosenfeld said. Another 15 were treated for minor injuries, he said.
Hamas praised the attack but did not claim responsibility.
"We told you #IDF that our blessed hands will reach your leaders and soldiers wherever they are," the al Qassam Brigades, the military wing of Hamas, said on Twitter. "You opened the Gates of Hell on Yourselves."
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U.S. Secretary of State Hillary Clinton shuttled from meetings with Palestinians to Israeli leadership Wednesday, after hopes of an imminent agreement between Hamas and Israeli leaders that could have halted the explosive carnage at least for a while dissolved Tuesday.
Clinton met early with Palestinian Authority President Mahmoud Abbas in Ramallah in the West Bank, according to the U.S. Embassy, and will sit down with Israeli Prime Minister Benjamin Netanyahu in Jerusalem for a second day.
U.N. Secretary-General Ban Ki-moon also met with Abbas in Ramallah Wednesday morning.
"Today the situation in Gaza is deeply alarming," Ban said, standing next to Abbas at a new conference. "Rockets aimed at military targets inside Gaza are killing and injuring civilians and damaging... civilian infrastructures."
Ban sadly recalled his visit in 2009 during the Israeli incursion into Gaza, Operation Cast Lead.
"It is quite painful for me as secretary-general and also personal(ly) as a human being to be back for the same reason," he said.
He demanded that diplomacy pave the way forward and called for the emergence of a Palestinian state.
Clinton is also to meet with Egyptian President Mohamed Morsy, who is working to broker a cease-fire.
Clinton is not expected to travel to Gaza, which is run by Hamas, considered a terrorist organization by the United States and other countries.
Pope Benedict, speaking from Vatican City, called Wednesday for both sides to end the violence.
"I feel the duty to reiterate once again that hatred and violence are not the solution to problems," he said.
Israeli television showed images of white smoke rising up from the bombed public transportation bus in Tel Aviv, but from the outside the vehicle appeared intact. At least one passenger was taken out on a stretcher.
An unexploded bomb was still on the bus, said Ofir Gendelman, spokesman for the Israeli prime minister.
At the scene of the bus bombing, police cordoned off the street as ambulances arrived.
There is a hospital nearby, said CNN's Sara Sidner. An eyewitness told her that the windows of the bus were shattered and a bomb squad has approached it.
Rumors of a suicide bombing circulated on social media and Hamas' TV station, but accounts by authorities and witnesses seemed to quickly dispel them.
"A bus explodes under my Tel Aviv office," said military spokeswoman Avital Leibovich on Twitter. "Possibly due to a bomb or suicide bomber. Hearing the sirens of the ambulances."
No one was found dead on the bus, according to authorities. Two people, speaking live on Israeli radio, said they witnessed the attack and that they saw a male throw a bag into the bus and then run away after the explosion.
Israel's Channel 10 reported that one suspect had been apprehended.
Hamas put its own spin on the attack in a banner on al-Aqsa.
"Hamas blesses the suicide bombing and assures that it is a natural response to the massacre of the al-Dalou family and targeting of innocent Palestinian civilians."
A rocket alarm howled over Ashkelon on the Israeli side shortly after 7:30 a.m. Wednesday, just minutes after Hamas' TV broadcaster al-Aqsa reported its militants' rockets striking there as well as in the towns of Sderot and Ashdod.
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Since midnight, 17 rockets out of Gaza have touched down in Israel, the IDF confirmed. The Iron Dome protection system intercepted 12 more.
CNN's Fred Pleitgen in Ashkelon heard two impacts but could not yet say if the rockets hit anything or were eliminated mid-air by the rocket defense system.
The Israel Defense Forces overnight targeted "dozens of terror infrastructure sites," including the Ministry of Internal Security, which it saw as Hamas' "main command and control center." It took aim at a police compound, a "military hideout," and other targets linked to what it called Hamas' "terror activity."
The Israeli military also struck a media building, where it said Hamas "deliberately located" an "intelligence operation center," and a system of tunnels used to transport fuel.
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Al-Aqsa said two of their journalists were killed when an Israeli strike targeted their car. The IDF confirmed the strike but said the two killed were Hamas operatives. Residents participated in a public funeral for the two.
The IDF also confirmed targeting bridges in central Gaza.
Gazan authorities have reported at least 139 people killed in the conflict as of Wednesday. Israel reported a total of five Israelis killed as of Tuesday.
According to the Gaza Ministry of Health, 27 people were killed Tuesday, including children. More than 1,100 people have been injured. It's not clear how many of the victims were militants.
More than 70 people have been injured in Israel, including soldiers, Israeli officials have said.
For hours at dawn Wednesday, state TV broadcast images of day breaking over Gaza City via a fixed camera. The scenes were deceptively serene. But recorded video inserted into newscasts showed bomb impacts, ambulances, a funeral, residents putting out a fire and rescuers digging through fresh rubble in the darkness to search for the living and the dead. The images hurled the stark reality of war into the sunrise skyline scene.
Hopes for an imminent calm between Israel and Hamas were briefly raised then dashed Tuesday, as diplomats rushed to try to restore peace.
Clinton offered Israel the unbending support of the United States at a press conference with Israel's prime minister late Tuesday. She and Netanyahu both stressed the desire for a lasting solution -- or "durable outcome" -- heard often recently in Jerusalem and Washington.
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"President Obama asked me to come to Israel with a very clear message: America's commitment to Israel's security is rock-solid and unwavering," Clinton said.
"Obviously, no country can tolerate a wanton attack on its civilians," said Netanyahu. "Now, if there is a possibility of achieving a long-term solution to this problem through diplomatic means, we prefer that. But if not, I'm sure you understand that Israel will have to take whatever actions necessary to defend its people."
Israeli spokesman Mark Regev has said that Israel is not interested in a temporary respite to give Hamas a chance to regroup, but instead wants a permanent solution.
There was a moment Tuesday when it looked like the attacks might stop. A senior Hamas official told CNN a "calming down" would be announced Tuesday night. But that did not happen.
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Similarly, Egypt's Morsy said Tuesday the "travesty of the Israel aggression on Gaza will end in a few hours." But a few hours passed, and Morsy's office told CNN not to expect any announcement.
A source familiar with discussions in Jerusalem told CNN, "One of the Israeli demands is that there should be a period of total calm for 24 hours before committing to any agreement."
Hamas has demanded an end to current embargoes and blockades.
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Ban Ki-moon met with Netanyahu Tuesday and later with Israeli President Shimon Peres.
The U.N. secretary-general had to take cover when sirens sounded in Jerusalem, warning of an incoming rocket, Jerusalem Mayor Nir Barkat said.
Military officials said the rocket landed in an open area of a village.
Israel has said it is holding off on a ground offensive into Gaza to give diplomatic efforts time.
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Tuesday's attacks included one aimed at Jerusalem, one that caused casualties in the southern town of Beer Sheva, and one that injured five Israeli soldiers.
Another rocket hit a civilian building in Rishon LeZion, part of metropolitan Tel Aviv, Israel Defense Forces spokeswoman Leibovich said.
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Hamas fired more than 30 rockets into the area in and around Beer Sheva, but most were destroyed by Israel's Iron Dome interceptors.
In Tel Aviv, a man with an ax attacked a U.S. Embassy security guard, Israeli police said.
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The Israel Defense Forces said it targeted 100 sites in Gaza Tuesday. Israel has sent at least 1,450 airstrikes to Gaza, counting the 100 strikes Wednesday.
The IDF dropped leaflets across parts of Gaza Tuesday warning residents to evacuate their homes and go to central Gaza City in efforts to minimize civilian casualties, Israeli officials say.
An Israeli airstrike hit a building that houses the local offices of Agence France-Presse in Gaza City. No one from the agency was injured, according to AFP.
Also in Gaza, CNN saw a group of men drag the body of another man through streets from the back of a motorcycle. The men, who carried weapons, yelled in Arabic that he was a traitor and Israeli spy.
Gaza has endured a crippling economic embargo since Hamas won control of the territory from the Fatah-led Palestinian Authority after a landslide 2007 election that was followed by intra-Palestinian clashes.
Many Arab and Muslim nations view Hamas as the victim of Israeli aggression.
Diplomats hope to avoid a repeat of 2008-2009, when at least 1,400 people died when Israeli troops invaded Gaza after a similar spate of rocket attacks.
CNN's Ben Brumfield, Dana Ford, Arwa Damon, Ben Wedeman, Christiane Amanpour, Mohamed Fadel Fahmy, Saad Abedine, Sara Sidner, Frederik Pleitgen, Kareem Khadder, Saad Abedine, Ingrid Formanek, Nicki Goulding, Neda Farshbaf, Marilia Brocchetto and Reza Sayah contributed to this report.