US officials to Cuban exile groups: stop violence here.

Top United States diplomatic and law enforcement officials want to send a message to anti-Communist Cuban exile groups in America: the tough anti-Castro line of the Reagan administration is not a license for violence here.

The government hopes it has successfully telegraphed its signal with the quiet arrest in New Jersey three weeks ago of a major anti-Castro activist, whom federal, state, and local investigators suspect to be a leader of the Omega 7 terrorist group. The group has taken responsibility for two murders and more than a dozen bombings with an anti-Castro theme over the past two years.

On the morning of Oct. 9, an FBI team led by Special Agent Tom Menapace arrested Armando Santana Alvarez in his West New York home and charged him with several counts of using a false US passport for travels throughout Latin America. Investigators say they later confiscated a large amount of marijuana and three handguns on the premises. He was arraigned in the US District Court in Newark, but the arrest warrant was issued in Puerto Rico, which was Santana's port of reentry into the US. He has since been released on bail.

''Everybody in the government saw it as a big, big arrest,'' says a senior State Department specialist on Cuban affairs. ''Armando Santana is clearly one of the most important guys in the hard-line, anti-Castro organizations in this country.'' The official adds: ''Any guys from the Cuban community who think they have been unleashed better take notice. Santana's arrest should be taken as a signal that breaking American laws will not be tolerated.''

The remarks appeared to be a reference to the repeated vows of US Secretary of State Alexander M. Haig Jr. to ''go to the source'' in Cuba to neutralize Castro's influence on revolutionary movements in Central America. Such intentions, the official implies, should not be interpreted by Cuban exile groups as approval for their violent campaigns in the US.

The stamps in Santana's passport, meanwhile, tell a curious story. Federal and local officials in a joint task force on terrorism who have examined it say that Santana had traveled to such countries as Chile, Argentina, Uruguay, and Paraguay over the past year in the company of a ''suspected arms dealer'' whom they refuse to identify at present.

According to an informed federal law official, the investigation that led to Santana's arrest originated with a surprising source: the Chilean secret police. The Chileans, according to this account, tipped off a US Central Intelligence Agency operative in Chile that he had traveled there, and the information was relayed to the FBI. The FBI then allegedly checked flight manifests and passports on file at the State Department until they discovered Santana's picture under the name of Alberto Liborno, a US citizen of Puerto Rican origins. Investigators said Santana had procured the passport, a New York driver's license, and Puerto Rican birth certificate on the black market without Liborno's knowledge.

A senior federal terrorist specialist labels Santana ''a recognized terrorist as heir apparent to the leadership of the Cuban Nationalist Movement. Under the attorney general's guidelines authorizing intense coverage of known terrorists, we covered him.'' Omega 7 is the name used to credit para-military manuevers by the Cuban Nationalist Movement.

''It has obviously got to be a major blow to them,'' adds another federal official who has tracked the Omega 7 group for years. Santana has been the head of the Cuban Nationalist Movement since 1978, which authorities blame for a number of assassinations and several bombings, he says. Omega 7 has taken credit for many of these.

The two New York area murders claimed by Omega 7 were a 1978 Sunday morning slaying of Eulalio Negrin, a Cuban exile who favored a ''dialogue'' with Fidel Castro, and the assassination last year in rush-hour traffic of Felix Garcia Rodriguez, a Cuban attache at the United Nations.

Armando Santana was asked whether he was the head of Omega 7, as alleged, in a 1979 New York magazine interview. He responded: ''I will not confirm it and I will not deny it. Why don't you bring me the proof?''

A native of Carderas, Cuba, Santana faces charges on each violation of the passport laws, which could lead to a $2,000 fine and five years in jail if he is convicted. New Jersey authorities could, say federal officials, bring charges stemming from the confiscation of marijuana and handguns. Santana's lawyer, Raymond Brown Jr. of Newark, was unavailable for comment.