Eleonora Antillon, a well-known Costa Rican journalist and TV presenter, told The Associated Press on Wednesday that Arias assaulted her in the mid-1980s when she was working for his fledgling presidential bid.
In a separate interview, Emma Daly, communications director for Human Rights Watch, said Arias groped her in a hotel lobby in Nicaragua in 1990 when she was working as a young journalist based in Costa Rica.
The New York Times also reported that a fourth woman, a 53-year-old book editor, alleged that Arias unexpectedly put his hand on her leg during a meeting in 2012. AP was not immediately able to confirm the report.
While the #MeToo movement swept up a number of powerful men in recent years in the United States, its spillover effect has been more muted in Latin America, where critics say macho attitudes die hard.
In Brazil, starting in December, more than 250 women accused a prominent spiritual healer of acts from unwanted fondling to rape, leading to his arrest and a raft of charges. In Argentina, accusations ranging from sexual assault to sexual harassment have been leveled against the likes of a well-known actor, a senator and a legislative chief of staff.
But none have had a profile like Arias, who was twice elected president of Costa Rica and in 1987 was honored with the Nobel Peace Prize for his work bringing an end to Central America's protracted and bloody civil wars.
The criminal complaint filed Monday in Costa Rica charged that Arias fondled a woman's breasts, kissed her and penetrated her with his fingers in December 2014 at his home in the capital, San Jose. The woman, a nuclear disarmament activist whose name was not released, had gone there for a meeting related to her cause.
In a brief statement Tuesday, Arias denied the allegation. He said he never violated the will of any woman and fought for gender equality during his career. He said he would not have further public comment because of the pending legal case.
As more allegations emerged Wednesday, his lawyer, Erick Ramos, echoed that, telling AP that "out of respect for the process that is in course, we are not going to make any kind of declaration."
Antillon, a renowned journalist and TV presenter known as "Nono," decided to break three decades of silence after the complaint became known this week.
She said she expressed disinterest in politics, but Arias insisted and didn't blink when she asked for a salary three times the going rate to try to discourage him.
"He laughed and said others were working for free, that later they were guaranteed a political job," Antillon said. "I said I wasn't interested, that if he wanted me he would pay me. And he laughed and looked at me and said that he would pay it."
After an agreement was struck, she said, Arias summoned her to a restaurant in San Jose where he met her in a private room. Almost immediately he put his hand on her thigh and tried to kiss her neck, she said. Antillon said she pushed him away and asked what he thought he was doing.
"'It's just to gain trust,' he told me, laughing," she said.
Antillon said she left, rejecting his offer to escort her.
Four days later she was with Arias and another adviser, but he sent the adviser away, she said.
"He stood up, he was at his desk, he came over staring hard at me, and he grabbed my hand and put it on his penis, over his pants," Antillon said. "I said to him, 'What are you doing?' and he said, 'What do you think we're doing? Look how hard I am.'"
Antillon said she recoiled, knocking over a chair, and Arias grabbed her shoulders, pushed her into an open closet and again placed her hand on his genitals. She pulled it away. Someone made a noise at the door, he composed himself and she left.
Afterward, Antillon said, she never allowed herself to be alone with Arias, whom she described as someone with "serious problems with arrogance."
"He sees himself as the master of the world, that everyone has to submit to him," Antillon said. "He sees himself as a conqueror."
Since then, Antillon said, she felt physically ill whenever she heard about Arias' Nobel prize. She said the experience left a mark and she has tried to dress in a less "feminine" way, not wanting to show much skin.
Only this week was she emboldened to come forward amid news of the complaint, she said.
"I believe her based on what I lived through," Antillon said of the woman whose complaint was filed this week.
Although it's been more than 30 years since the incidents she described to AP, Antillon said if any lawyer could find a way to bring a complaint against Arias, she would be willing to do so.
AP normally does not use the names of alleged victims of sexual assault, but both Antillon and Daly came forward to tell their stories publicly.
Speaking to AP in New York, Daly said she had been in Costa Rica for a couple of years when her encounter with Arias happened in February or April of 1990 in neighboring Nicaragua. At the time she was in her mid-20s, working for an English-language weekly in Costa Rica and stringing for Reuters.
The lobby of the Intercontinental Hotel was packed with journalists and diplomats when she saw Arias, with whom she had established a cordial relationship in her role as a political reporter, Daly said. They had first met years earlier through her parents, who were diplomats, she said. She called out to him and asked a question.
"And instead of answering my question, he stopped and looked at me and leaned forward, and he put his hand on my chest and sort of pulled it down between my breasts and then said, 'You're not wearing a bra' — or words to that effect," Daly told AP.
"I was so shocked, all I could think of to say was, 'Yes I am wearing a bra,' which is a ridiculous reaction but that's what I did in the moment, and he walked on," she continued. "A woman next to me, another reporter, said to me: 'I saw what happened. I'll support you if you want to do something.' And I said, 'No, that's fine, forget about it.'"
Daly said part of what was upsetting was that it came in a professional setting, surrounded by politicians and journalists.
"You're completely ignored from a professional side, but someone touches you and you're made to feel as if you're nothing, they can do whatever they want," she said.
Daly said Arias had never done anything like this in any prior interaction with her, nor had she seen him do anything to anyone else. She felt the overall environment was one of machismo, and if she complained nothing would happen.
She said she felt angry and then humiliated that she "hadn't responded properly, but I didn't really see what I could do or where that could lead. If I had gone to complain about it, I felt I would have been laughed out of whatever office I tried to complain to."
Daly said she told her then-boyfriend as well as several other people about the incident. She doesn't remember seeing Arias again. He left office not long after, and she left the region.
But she said she began thinking about the incident more amid the rise of #MeToo, making an oblique reference to "Even a president and Nobel laureate" in a comment on a friend's Facebook post in October 2017. She said she thought about naming Arias at the time but decided not to.
Daly first told her story publicly to a Washington Post reporter who reached out to her Tuesday.
She said she felt she was in a privileged place — she wasn't going to lose her job, her family support — so it was important to speak out.
She said the difficult thing is that Arias has done good work in his professional life, with the peace plan, but that doesn't give him a pass to mistreat people.
"It would be really wonderful if this spurred some kind of a reckoning in Latin America with men who harass women," Daly said, "particularly at work ... some kind of moment where they understood that there's a need for systemic change and it's really not OK to just touch women because you feel like it."
Arias' National Liberation Party announced in a statement Thursday that he was leaving the party pending an outcome of the criminal case.
On social media, users have been posting messages of support for the women using the hashtag "yotecreo," which means "I believe you."
Associated Press writer Javier Cordoba reported this story in San Jose, Costa Rica, and AP writer Deepti Hajela reported from New York.