A proposed police investigation into the alleged role of Israel's internal security chief in the beating death of two captured Arab hijackers has spotlighted the clash here between the commitment to the rule of law and the demands of Israeli security.

It also could raise questions about the role of former prime minister Yitzhak Shamir at the time of the incident and the actions of Prime Minister Shimon Peres in the handling of its aftermath.

A week-long national and media debate over the issue has begun to subside -- at the rhetorical level, at least -- but there remain unanswered questions of how much was known about the security service chief's role in the case and when it was known by the two senior ministers.

Peres and Shamir have adopted a common stand against a formal police investigation, saying that public disclosure could jeopardize the security service and, ultimately, national security.

It also presumably would jeopardize the unified position taken by the two political rivals in defense of Avraham Shalom, the chief of the Shin Bet, or secret security service, and lead to public official comment on persistent reports in the Israeli press that Shalom -- aided by the prime minister's office -- led a concerted effort to cover up his role in the deaths of the two hijackers after they had been taken into custody.

Shamir was prime minister when Israeli security forces stormed a hijacked bus in the Gaza Strip on April 14, 1984, and led two surviving Palestinian hijackers to a nearby field where both were pistol-whipped to death while handcuffed, according to two commissions of inquiry.

Cabinet Minister Ezer Weizman last night suggested that Shamir knew details of the incident when he was prime minister and said that he should appear before an inquiry panel to disclose his role in the affair. In an interview on Israel Television, Weizman said, "If the Shin Bet did it without letting Shamir know, it is twice as serious." Weizman said he believed that Shamir had suppressed the information.

Shalom has been targeted by Attorney General Yitzhak Zamir for a police investigation on suspicion of ordering the security forces to kill the suspects and then later destroying evidence, suborning witnesses and committing perjury in an effort to cover up the incident.

Traditionally, the head of the Shin Bet is responsible only to the prime minister.

Peres' personal interest in the case, according to informed Israeli sources, stems from a visit to his office more than six months ago by three of Shalom's senior deputies, who presented him with allegations of a cover-up by the Shin Bet chief. When Peres backed Shalom on the matter, the three security aides presented their case to Zamir, who then began pressing for a police investigation of Shalom's actions during the bus siege and afterward.

The three Shin Bet officers subsequently were forced out of the secret security service. The secrecy surrounding the case began to unravel when one of them, Reuven Hazak, filed a complaint with Israel's High Court that he had been improperly dismissed.

Disclosure of Zamir's insistence on a police investigation and prosecution of Shalom triggered an emotionally charged national debate. One side has insisted that no public official, even at the risk of compromising security, can be held above the law. The other argues that Israel's unique position as a small and vulnerable country surrounded by Arab enemies requires it to have a secret security service that at times can operate outside the law.

"Only the government has the authority to decide about policy in the war against terror," declared Trade Minister Ariel Sharon. " . . . This is not a matter of democracy or the rule of the law; this is a matter of the existence of the State of Israel."

Similarly, Labor Minister Moshe Katzav said that Israel is in a state of war against terrorism, adding, "In a state of war the normal laws don't apply. The Shin Bet, indeed, violates some of the basic laws. This must be recognized and legitimatization given to it."

Communications Minister Amnon Rubenstein, of the Shinui Party, argued for an investigation of Shalom, saying that the law would protect any classified information unearthed by the probe, while Labor Party Knesset member Abba Eban declared, "If we want death sentences for terrorists, then surely the honor should go to the Knesset" to pass a capital punishment law.

The Hebrew daily, Yediot Aharonot, today published the results of a public opinion poll in which it asked respondents which should prevail when there is a conflict between the rule of law and security considerations. Seventy-three percent favored security considerations and 23 percent said the rule of law should prevail, according to the newspaper.

Both Peres and Shamir are adamantly opposed to an investigation of the security services chief, saying that it could inflict incalculable damage on Israel's domestic intelligence network by disclosing the identities of its agents, its structure and operational procedures.

However, both have acknowledged the division of authority between the executive and the judiciary, and Peres has said that once Zamir decided to press ahead with a police investigation, the question was outside the authority of the government. For his part, Shamir has suggested diluting the power of the attorney general so that similar conflicts cannot arise in the future.

The political liability to both Peres and Shamir if a police investigation goes forward is that both could end up being accused of participating in a cover-up of Shalom's alleged role in the deaths. Peres allegedly did not act when the three Shin Bet aides brought the allegations to him six months ago, and Shamir allegedly did nothing when, according to official sources, he received a detailed, confidential report from the Shin Bet shortly after the incident.

A military disciplinary board last August tried the Army's chief infantry and paratroop officer, Maj. Gen. Yitzhak Mordechai, on charges of "violent behavior" and conduct unbecoming an officer in connection with the deaths. The board ruled that injuries caused by Mordechai with the butt of his pistol were "not unreasonable" because the security forces had been attempting to obtain information about a bomb planted aboard the hijacked bus.

Both hijackers died shortly afterward of skull fractures.

Neither Peres nor Shamir has yet offered detailed explanations of how much they knew about Shalom's alleged role in the killings or when they first heard of the allegations.

Shamir, in an interview yesterday on state-run Radio Israel, said, "I don't have to tell anyone what I knew or what I didn't know. I knew what a prime minister has to know, and I acted accordingly."

The former prime minister, who is scheduled to rotate into the premiership in October under the "National Unity" coalition agreement, added, "No one here did anything wrong. The disclosure did wrong. The [security] organization must continue functioning, and therefore this subject must be taken off the public stage."

Peres, also interviewed, was asked if the political leaders approved either the killing of the hijackers or a cover-up. "First of all," he replied, "nothing has been proved yet, and therefore one can't talk about approval from this level or that. Naturally, the present prime minister does not check the actions of his predecessors."

Asked whether he obtained information about the case when he succeeded Shamir in September 1984, Peres replied, "Not only did I not get any, I never thought to ask, because I'm not dealing with history."

The common stand adopted by the long-time political rivals, backed by a majority of the coalition Cabinet, so far has averted the kind of coalition crisis that could lead to the breakup of the government and new parliamentary elections.

But there have been persistent reports in the Israeli press of a detailed letter written to Shamir by Shalom that outlines the security chief's role in the storming of the hijacked bus and its aftermath. If the reports are verified by evidence made public during a new investigation, the senior ministers' unity on the issue could begin to unravel. Shamir has neither confirmed nor denied that such a letter exists.