TEL AVIV, OCT. 19 -- A terror bombing on a crowded commuter bus tore through the commercial center of Tel Aviv at the height of this morning's rush hour, killing at least 20 people and prompting Israel to seal its borders with the Gaza Strip and West Bank.

The explosion, an apparent suicide attack by a passenger, mangled the bus, damaged another passing in the opposite direction and shattered shop fronts near Dizengoff Square on Tel Aviv's main shopping boulevard at 9 a.m. (3 a.m. EDT). Police said at least 48 people were wounded, some maimed or seriously burned.

Rescue and burial teams worked for hours to collect the casualties in a grisly scene of blood and destruction. The red-and-white No. 5 bus, which wound a route from the central terminal through downtown Tel Aviv, was little more than a blackened skeleton. The other bus, which absorbed some of the blast, stood immobilized, its windshield shattered.

The attack was the third claimed by the Islamic Resistance Movement, or Hamas, in 10 days; the death toll was the heaviest in violence between Israelis and Palestinians since February, when a Jewish extremist killed 29 Arab worshipers at the Tomb of the Patriarchs mosque in the Israeli-occupied West Bank town of Hebron.

Israeli Prime Minister Yitzhak Rabin, who rushed home from a visit to Britain after the bombing, vowed harsher measures against Hamas suspects and their families and again demanded a similar crackdown by Yasser Arafat's limited self-rule authority in Gaza and the West Bank town of Jericho.

Arafat, who has put his leadership on the line to continue the peace process with Israel and is struggling with rejectionists in Hamas, denounced the attack, which coincided with the return of Israeli and Palestinian negotiators to talks on self-rule in the West Bank. Israel Defense Forces Radio reported that Arafat tried to place a condolence call to Israeli President Ezer Weizman but that Weizman refused to come to the phone.

Rabin stood firm against domestic critics of continuing peace talks with Arafat. After opposition leaders demanded a halt to the talks and permanent Israeli dominion over the occupied Arab territories, Rabin used a late-night television appearance to call for clearer partition between Israelis and Palestinians.

"Israel today wants separation, not a {temporary closure of borders}, but a different way of life," he said from his office at Tel Aviv's Defense Ministry. "What will be the future -- separation or a continued blurring of the lines? He who wants to swallow 2 million Arabs into Israel, that will be giving Hamas the maximum support."

About 28,000 residents of Gaza cross into Israel daily to work at construction and agricultural jobs. Rabin said Israelis should reduce their dependency on cheap Palestinian labor, and he portrayed the self-rule talks as a way to create territorial lines that neither side would cross. He appeared to be saying, in effect, that Palestinians should not live and work among Israelis, nor Israelis among Palestinians.

Arafat, in an apparent reference to Iran's role keeping Middle East tension alive, said: "Pushing forward with the peace process and implementing the rest of the agreement is the only way to respond to the enemies of peace who are getting their support, their training and financing from well-known outside parties," the Associated Press reported.

In Washington, President Clinton, who is scheduled to visit Israel next week, called the bombing "an outrage against the conscience of the world."

It was unclear tonight whether domestic backlash over today's attack, which follows a machine-gun assault on a Jerusalem pedestrian mall and the abduction and killing of a 19-year-old Israeli soldier, will limit Rabin's room to maneuver.

In the heat of their anger, many Israelis interviewed today expressed frustration with the fruits of peace and Rabin's strategy for securing citizens against attack.

"Look, I voted for Labor, but I'm a little sorry about it," said Dmitri Karamazen, 20, a soldier who hovered protectively over his unconscious girlfriend, Stanislava Shmakin, after she was brought from the bombing site to Tel Aviv's Sourasky Hospital. "They're not showing their strength; they're not using their force the way they should so these things won't happen. {Former Likud prime minister Yitzhak} Shamir didn't do enough for peace, but during his time we didn't have incidents like this."

Opposition leaders -- who rallied around Rabin last week as the nation waited to learn the fate of Cpl. Nachshon Waxman, the abducted soldier who was ultimately slain -- blamed Rabin today for the bombing attack in harsh and personal terms.

"I told him not to lift the closure {of Gaza last week} because it would result in a catastrophe," Likud leader Binyamin Netanyahu said in an interview on Dizengoff Street, where he strode grimly through the carnage. "It has just resulted in a catastrophe. There is no difference between Hamas and the PLO; they both want a Palestinian state as a prelude to our destruction."

Neither Netanyahu nor official government accounts identified the person who carried out the bombing or his place of residence. But Netanyahu, and to some extent Rabin, have charged that Gaza is the nerve center of Hamas and its military operatives.

"It's very wrong to say these people are trying to murder the peace," said Alon Tsabari, 29, who helped pull some of the injured to safety. "They are trying to murder Jews. They have been doing it for more than 100 years."

In claims of responsibility telephoned to radio stations and broadcast from loudspeakers atop Gaza's Palestine Mosque, Hamas boasted that it had learned the art of making car bombs as a result of the deportation of some of its key members to southern Lebanon in 1992. A Hamas leaflet said the man who built the bomb was Yehiya Ayash, from the West Bank town of Rafat, who has been wanted by Israeli authorities for two years.

"If you go to the street in Gaza and look at the faces of the people, you will find smiles," said Fayed Abu Shamala, a local Hamas leader.

Some Israeli officials warned of vengeance to come. Foreign Minister Shimon Peres said Israel will "not hesitate to find those responsible for this terrible action." Weizman, a former air force chief of staff, said the country will have to take "extraordinary action" to locate the roots of Islamic extremist groups and "rip them to pieces."

Rabin, too, spoke of cracking down on Hamas, and he asked for the easing of legal restraints on Israeli security forces in dealing with terror suspects. Noting that the Shin Bet intelligence service had captured and interrogated the driver of the car in which Waxman was abducted, Rabin spoke dismissively of a 1987 commission report calling for a ban on torture of suspects but permitting "moderate physical and psychological pressure."

"If we'd been so careful to follow the Landau Commission, we would never have found out where Waxman was being held," Rabin said. Waxman's captors shot him to death as Israeli commandos raided their hideout in Bir Nabalah in the West Bank.

Rabin said he would seek legislation to permit greater latitude in interrogations and wider use of collective punishment -- particularly demolition of homes of relatives and associates of Israel's attackers. "I want them to know that they're risking not only their own lives, but also their family's homes," he said.

Human Rights Watch, a U.S.-based group, said tonight that it is "gravely concerned" that Rabin's proposals could "cause a severe deterioration in the human rights situation in the occupied lands."

But perhaps the most striking theme in the government's response was that of national separation. Lt. Gen. Ehud Barak, the army chief of staff and a close Rabin ally, told Israeli television it is perhaps time to "reexamine the entire set of our relations with the Palestinians, which allow daily tens of thousands of Palestinians to come to and from Israel to work. Clearly if there are no Palestinians who work in Israel, it will be more difficult" for terrorists to infiltrate.

Some major terror attacks mounted by Hamas against Israelis or Israeli targets:

July 6, 1989: A Hamas supporter grabbed the wheel of an Israeli bus and steered it into a ravine, killing 16 passengers and injuring 26.

Dec. 15, 1992: The bound body of Israeli policeman Nissim Toledano was found after being kidnapped by Hamas in an effort to force the release of its jailed leader, Sheik Ahmed Yassin. Two days later, Israel rounded up 415 alleged Hamas activists and deported them to Lebanon.

July 1, 1993: Two Israeli women were killed when Palestinian gunmen thought to be members of Hamas opened fire inside a commuter bus. Two of the gunmen were later killed in a clash with police.

April 6: A Hamas suicide bomber killed eight people in the town of Afula in retaliation for the attack by a Jewish extremist on the mosque in Hebron containing the Tomb of the Patriarchs, sacred to both Arabs and Jews. Twenty-nine Arabs died in the attack.

April 13: A Hamas suicide bomber killed five people in the town of Hadera.

Oct. 9: Two Arabs sprayed Jerusalem's restaurant row with gunfire, killing two bystanders and wounding 14. Hamas claimed responsibility.

Oct. 9: Islamic militants from Hamas kidnapped an Israeli soldier, Cpl. Nachshon Waxman, and threatened to kill him unless Israel freed Sheik Yassin and other jailed Muslim fundamentalists.

Friday: The militants killed Waxman, 19, when Israeli commandos raided their West Bank hideout. An Israeli commando and three Islamic militants also died.

Yesterday: A terrorist bomb shattered a bus in the heart of Tel Aviv's shopping district in apparent suicide attack claimed by Hamas. At least 20 people were killed and 48 wounded.

SOURCES: Associated Press; Reuter