Updated 10:30 a.m. Eastern
TEL AVIV, Israel A bomb exploded aboard an Israeli bus near the nation's military headquarters in Tel Aviv on Wednesday, wounding 27 people and delivering a major blow to diplomatic efforts to forge a truce to end a week of fighting between Israel and Gaza's militant Hamas rulers.
The attack came as diplomats, including U.S. Secretary of State Hillary Rodham Clinton, shuttled around the region to try to broker a cease-fire following a week-long Israeli offensive against Palestinian militants in Gaza that intensified to its most feverish state overnight, according to CBS News correspondent Charlie D'Agata. Palestinian officials say more than 140 people have been killed, and 1,000 wounded -- most of them civilians, and many children among them.
Israeli aircraft pounded Gaza with at least 30 strikes overnight, hitting government ministries, smuggling tunnels, a banker's empty villa and a Hamas-linked media office. And it took Israel less than two hours to respond to the bus bombing with a fresh round of air strikes on the tiny Palestinian territory. As night fell in the Middle East, D'Agata says at least 30 shells from an Israeli warship pounded the city.
One blast the night before blew out the windows of the hotel room where D'Agata was staying in Gaza.
Militant rocket fire into Israel has killed five Israelis.
This, as thousands of Israeli ground troops massed on the Gaza border awaiting a possible order to invade.
The bus exploded about noon on one of the coastal city's busiest arteries, near the Tel Aviv museum and across from an entrance to Israel's national defense headquarters.
The bus was charred and blackened, its side windows blown out and its glass scattered on the asphalt. The wounded were evacuated and blood was splattered on the sidewalk.
An Israeli driver who witnessed the explosion told Army Radio the bus was "completely charred inside." Another witness said there were few passengers on the bus when it exploded. The witnesses spoke to Israeli TV and were not identified.
The last bombing in Tel Aviv was in April 2006, when a Palestinian suicide bomber killed 11 people at a sandwich stand near the city's old central bus station. A bomb left at a bus stand in Jerusalem last year killed one person.
While Hamas did not take responsibility for the attack, it praised the bombing.
"We consider it a natural response to the occupation crimes and the ongoing massacres against civilians in the Gaza Strip," Hamas spokesman Fawzi Barhoum told The Associated Press.
Clinton, meanwhile, pressed on Wednesday with efforts to wring an elusive truce deal from Israel and Gaza's militant Hamas rulers, after earlier attempts to end more than a week of fighting broke down amid a furious spasm of violence.
She joined other world diplomats in shuttling between Jerusalem, the West Bank and Cairo, trying to piece together a deal that would satisfy the two foes after a week of fighting and mounting casualties.
After meeting with Israeli Prime Minister Benjamin Netanyahu in Jerusalem Tuesday night, Clinton conferred with Palestinian President Mahmoud Abbas in the West Bank on Wednesday morning, then arrived in Cairo, where the new Muslim Brotherhood-led government is mediating in the crisis.
Clinton met Egyptian President Mohammed Morsi, and was to sit down later with Foreign Minister Mohamed Kamel Amr, and Arab League Secretary-General Nabil al Araby.
The two sides had seemed on the brink of a deal Tuesday following a swirl of diplomatic activity also involving the U.N. chief and Egypt's president. But sticking points could not be resolved as talks -- and violence -- stretched into the night.
At least four strikes within seconds of each other pulverized a complex of government ministries the size of a city block, rattling nearby buildings and shattering surrounding windows. Hours later, clouds of acrid dust still hung over the area and smoke still rose from the rubble.
The impact of the blast demolished the nearby office of attorney Salem Dahdouh, who was searching through files buried in the debris.
"Where are human rights?" he asked, saying officials negotiating a cease-fire ought to see the devastation.
In downtown Gaza City, another strike leveled the empty, two-story home of a well-known banker and buried a police car parked nearby in rubble.
"This is an injustice carried out by the Israelis," said the house's caretaker, Mohammed Samara. "There were no resistance fighters here. We want to live in peace. Our children want to live in peace. We want to live like people in the rest of the world."
The Israeli military said its targets included the Ministry of Internal Security, which it says served as one of Hamas' main command and control centers, a military hideout used as a senior operatives' meeting place and a communications center.
Washington blames Hamas rocket fire for the outbreak of violence and has backed Israel's right to defend itself, but has cautioned that an Israeli ground invasion could send casualties soaring.
Israel's outspoken foreign minister, meanwhile, expressed what many in Israel suspect - that ahead of January elections, the country's leaders do not want to get mired in a ground operation.
"There is no point embarking on such a dramatic move two months before elections after we didn't do it for four years," Foreign Minister Avigdor Lieberman told the Ynet web site Tuesday. Israeli government spokesman Mark Regev had no comment on Lieberman's remarks.
Hamas official Izzat Risheq predicted a truce deal would be reached Wednesday, but the movement wouldn't discuss what the problems were.
Israeli media quoted Defense Minister Ehud Barak as telling a closed meeting that Israel wanted a 24-hour test period of no rocket fire to see if Hamas could enforce a truce among its forces and other Gaza militant groups.
Palestinian officials briefed on the negotiations said Hamas wanted assurances of a comprehensive deal that included new arrangements for prying open Gaza's heavily restricted borders, and were resisting Israeli proposals for a phased agreement. The officials spoke on condition of anonymity because they were not authorized to talk to the media.
Israel launched the offensive on Nov. 14 following months of rocket salvoes from the territory into southern Israel, which has endured attacks for the past 13 years. For its opening salvo, it assassinated Hamas' military chief, then followed up by bombarding the militant-run territory to its south with more than 1,500 airstrikes that initially targeted rocket launchers and weapons storage sites, then widened to include wanted militants and symbols of Hamas power.
Defying Israel's claims that they've been badly battered, the militants have so far fired more than 1,400 rockets at Israel, drawing upon newly developed and smuggled weapons to extend the reach of their attacks toward Tel Aviv and Jerusalem, Israel's largest cities. The number of Israelis within rocket range leapt to 3.5 million from 1 million.