How does an embassy press secretary get labeled "Mata Hari" overnight? Ask Angela Saballos.

On Monday, Saballos was busy typing at her desk at the Nicaraguan Embassy when a free-lance photographer came by to take her picture. She says she'd been told by a New York photo news agency that the embassy merely wanted a photo of her for its files. It seemed odd to her, she says, but she looked up from her typewriter, anyway, half-smiling into the camera lens.

"CIA PROBES D.C. 'MATA HARI' " screamed the next day's front-page headline in the New York Post, the frequently lurid tabloid owned by international press baron Rupert Murdoch. Underneath was a large picture of Saballos, accompanied by a caption that read: "An internal Central Intelligence Agency report, disclosed to The Post, says Miss Saballos was trained by Cuban intelligence. It also expresses concern over her alleged ties with two Democratic members of Congress." A story on Page 2, written by Washington correspondent Niles Lathem, describes her as "suspected" of being "at the center of an intricate Sandinista spy operation."

The CIA says it has no comment on the existence of any report, although a spokesman adds: "If you get your hands on it, we'd like to see it, too."

Saballos, meanwhile, is enraged.

"I think I was--how should I say it?--stupid. Not precisely stupid, but coming from the provinces. I feel like I was showering and somebody entered the bathroom. It's a dirty trick. I never spoke with them." The embassy has issued a statement saying Saballos was "slanderously attacked" and asks that the New York Post "publicly retract all these false imputations."

"We stand by the story 1,001 percent," says Steve Dunleavy, the New York Post's metropolitan editor. "We obviously wouldn't have written it without some extremely substantial proof." He wouldn't say how her picture had been taken, and the photographer, Tim Dillon, wouldn't say who had given him the assignment.

Saballos, 38, has been in Washington for a year. She is divorced and lives in Chevy Chase with her two children. She was a reporter for the Nicaraguan newspaper La Prensa when it was the focus of opposition to former President Anastasio Somoza. (Ironically, now La Prensa is opposed to the Sandinistas.) Her job is to dispense information, primarily to reporters, about the Sandinista government in Nicaragua, and to counter the Reagan administration's position that it is a government under Soviet and Cuban influence.

It is well known in intelligence circles that the United States has the capacity--and the authority--to wiretap those foreign embassies whose intelligence operations are determined by the CIA director to be hostile to the United States. Saballos, in her conversations with Washington reporters, routinely asks her own questions about events on Capitol Hill and other general news around town. This is standard procedure for embassy press officials, who frequently send the information back to their governments.

"This happened not because it was me," says Saballos. "It happened because it was Nicaragua. This is not coming out of the blue sky. I would say this is a plant of covert operations. You know how I feel? People in Nicaragua are being killed on the border. I felt as if they were trying to kill me as a person here. It's a feeling of war going on over here. And they're trying to portray me as a sex bomb or something like that."

On Wednesday, there appeared another story about Saballos under this headline: "Angela, a madder Hari, says 'I no spy.' " It quotes her as saying to the New York Post's Tom Checchi: "I have a boring social life in Washington," and also, "I only get bothered by dirty old men."

"He hasn't spoken to me," she says. "But if he did, I suppose he'd ask, 'Is it true, are you a Mata Hari?' "

Mata Hari, a 19th-century Dutch dancer whose real name was Gertrude Margarette Zelle, danced on the French stage. She developed a repertoire of sultry dances, had affairs with prominent French and Dutch officials and was a spy for the Germans during World War I. She was killed by a French firing squad in 1917.