TEL AVIV -- A blast, a plume of smoke, the smell of gunpowder and a blown-up bus -- scenes that had begun to fade from the collective Israeli memory came back in sharp relief on Wednesday, along with a renewed sense of vulnerability, when a bomb exploded on a passenger bus just after midday, injuring more than 20 people in the heart of Tel Aviv.
The residents of this Mediterranean city have often been derided by other Israelis of existing in a "bubble" of beaches, fashionable restaurants and bars. But that sense of isolation faded as the city suffered its first terrorist bombing in years.
Even as Israeli and Palestinian officials announced a cease-fire on Wednesday, halting eight days of Hamas rocket attacks and Israeli airstrikes, the cross-border conflict extended its physical and psychological reach.
A decade ago, the crude Qassam rockets from Gaza reached as far as Sderot, the Israeli town about a mile from the Gaza border. But in this conflict, nearly half the Israeli population found itself vulnerable to fire.
In recent days, after Israel embarked on a military offensive meant to stop the persistent rocket fire that has plagued the south, air raid sirens sounded more than 40 miles away in Jerusalem and Tel Aviv. Most of the rockets fired at those cities were either intercepted or fell harmlessly in open ground or off the coast. But on Tuesday, a rocket with a powerful warhead destroyed the top three floors of an apartment building in Rishon LeZion, a suburb of Tel Aviv about seven miles south of the city. "They are pursuing us," said Marcelle Azulai, a resident of Tel Aviv who had been sitting on a bus behind the one that was bombed.
Nobody was killed in the bombing, although health officials at the nearby Ichilov Hospital said that 21 people were treated for injuries, including two teenagers in more serious condition, and the rest with moderate or light injuries.
"This was a lucky one," said Dr. Pinchas Halperin, who runs the hospital's emergency room. Judging by the relatively small amount of shrapnel, he said, the bomb that went off on Wednesday appeared to be smaller than those that traumatized Israelis after the second Palestinian uprising broke out in 2000. In the following years, hundreds of Israelis were killed by suicide bombings and shooting attacks on buses and in cafes and shopping centers.
The latest bombing brought some of that terror back. The police said a man had apparently boarded the bus, placed the bomb in a bag under a seat and disembarked shortly before it exploded. Helicopters circled for hours after the blast, and police set up roadblocks as they hunted for the perpetrator, whom they suspected might have come from the West Bank.
"At first we thought a rocket had fallen without a warning siren," said Moran Cohen, 24, a student who was working in a restaurant near the scene of the attack. "People started running. The fear is back."
On the sidewalk outside the hospital, two youths were operating a stand in the name of the Chabad-Lubavitch organization of Hasidic Jews, offering male passers-by the opportunity to put on tefillin, the small leather boxes containing scripture verses, and to recite psalms.
Some residents of the city were defiant and said they would not change their routines. But others acknowledged that for them, something had changed.
"When the siren went off here for the first time on Friday, I left work and went home in fright," said Tomer Calderon-Vaisman, 33, who runs a restaurant in Tel Aviv. "Now I try to be in places where I feel safe."
Mr. Calderon-Vaisman and his wife, Galia, 31, an architect, had come to the hospital when a friend called to say that she had been injured in the bus bombing.
"Let's say it makes you think a lot," Ms. Calderon-Vaisman said. "It is the worst weapon that there is. There is no siren to warn you. You are living your life and in one second they can take it from you. In one moment your life can end because you boarded a bus."
This article originally appeared in The New York Times.