Updated Thursday, November 22, 2012 at 05:24 PM
TEL AVIV, Israel — A blast, a plume of smoke, the odor of gunpowder and a blown-up bus, scenes that had begun to fade from the collective Israeli memory, returned Wednesday, when a bomb exploded on a passenger bus, injuring more than 20 people in the heart of Tel Aviv.
The residents of the 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 Wednesday, 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 began 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, who had been sitting on a bus behind the one that was bombed.
Nobody was killed in the bombing, although officials at the nearby Ichilov Hospital said 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 emergency room.
Judging by the relatively small amount of shrapnel, he said, the bomb that went off Wednesday appeared to be smaller than those that traumatized Israelis after the second Palestinian uprising began in 2000. In the subsequent years, hundreds of Israelis were killed by suicide bombings and shootings on buses and in cafes and shopping centers.
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 attack. "People started running. The fear is back."
DAN BALILTY / AP
Israeli police examine a destroyed bus at the site of Wednesday's bombing in Tel Aviv, Israel. No one died, but nearly two dozen people were injured.