CIA officials, before distributing a manual advising rebels in Nicaragua about guerrilla techniques, censored all but a few copies but did not remove recommendations that violence be used to "neutralize" Nicaraguan government officials, two senators said yesterday after a Central Intelligence Agency briefing.

The announcement by Sens. Malcolm Wallop (R-Wyo.) and Sam Nunn (D-Ga.) contrasts with the impression left by President Reagan in Sunday's presidential debate. That included a question on whether his administration was supporting terrorism by distributing a manual advocating assassination of Nicaraguan officials, hiring criminals and creating martyrs by killing some rebels.

Reagan said that only 12 uncensored copies of the 90-page handbook "got out down there and were not submitted" for censorship. Those responsible for "the few that did not get excised or changed . . . will be removed," Reagan said, citing possible violations of his December 1981 executive order banning political assassinations.

However, Nunn and Wallop said the censored portions did not include the section entitled "Selective Use of Violence" that has caused most of the controversy.

In that part, the booklet says, "It is possible to neutralize carefully selected and planned targets, such as court judges . . . police and State Security officials." It stresses the need to make sure that the local population understands the need to "replace the target" individual.

"The term 'neutralization' was in all the documents," Nunn said. "It should not have been published or distributed by the CIA."

The censored parts referred to hiring criminals and creating martyrs, according to some of those at the three-hour CIA briefing. Wallop, appearing with Nunn afterward, noted that "neutralization" did not necessarily mean "assassination," a word not used in the manual.

Nunn agreed but added that, when read in context, "it could lead one to the conclusion that the president's policy on assassinations was being or could possibly be breached."

Democrats seized on the issue when the manual surfaced last week, citing it as evidence that Reagan's goal in Nicaragua is to overthrow the leftist Sandinista government, not merely stop Nicaragua from sending arms to leftist rebels in El Salvador.

Wallop and Nunn, the only members of the Senate Select Committee on Intelligence in town for the briefing, said that many questions remain unanswered and that the CIA briefers were new to the issue and not as well informed as they could have been.

But Wallop said he saw "no indication of foot-dragging" and insisted that the document did not cast doubts on Reagan's policy.

"I do not believe that it calls for the overthrow of the government. It calls for the establishment of democracy, which the Nicaraguan government says that it is about to try to do," he said. Presidential elections there are scheduled Nov. 4.

According to others at the briefing, the CIA explanation conflicted in part and agreed in part with the account given journalists last week by Edgar Chamorro, a member of the directorate of the largest Nicaraguan rebel group, the Nicaraguan Democratic Force (FDN).

The CIA, Chamorro and Reagan agreed that the manual was written by a low-level CIA contract employe, who FDN sources said called himself John Kirkpatrick. Chamorro said that, as propaganda director, he received 2,000 copies of the manual and personally deleted sections on hiring criminals and creating martyrs because he found them offensive.

The section on "neutralization" was left in.

Reagan said during the debate that a CIA official in Central America "recognized that what was in that manual was in direct contravention of my own executive order" and had it censored.

The CIA told Wallop and Nunn that all but 24 copies were censored and that 12 of those were recovered, according to some of those present. That tallied with Reagan's observation that 12 copies escaped censorship "some way or other."

The CIA officials said a second printing of the manual, not the first, involved more than 2,000 copies, those present said.

They said the briefers, referring to the deaths Friday of four CIA employes in a plane crash in El Salvador, assured Wallop and Nunn that the plane's mission did not involve Nicaragua.

They said the briefers also discounted a Defense Intelligence Agency document, which was dated July 16, 1982, and reported "assassinations" by Nicaraguan rebels, calling some of them terrorists.

The publication, entitled "Weekly Intelligence Summary," had so little importance and was seen by so few people that it has since been discontinued, the briefers said. The information that rebels were killing Nicaraguan officials despite Reagan's 1981 order may not have been accurate and probably never reached high officials, they said.

In a related development, FDN spokesman Bosco Matamoros said here that Chamorro "is no longer authorized to speak for the FDN."

He admitted "abuses" during the four-year rebel effort but said those responsible have been punished. "That the manual exists does not mean we put it into practice," he said. "The ones who practice assassinations are the Sandinistas."

Meanwhile, U.N. Ambassador Jeane J. Kirkpatrick dismissed as "irresponsible" a Newsweek magazine report that members of her staff debated the need for such a guerrilla guide to help the rebels a year ago.