MIAMI, United States (AP) — The head of the Organization of American States is facing an internal investigation into allegations he carried on an intimate relationship with a staffer that may have violated the organisation's code of ethics, The Associated Press has learned.

News of the probe into a relationship between Secretary General Luis Almagro and a Mexican-born woman two decades his junior emerged as Almagro and delegates from 34 countries gathered in Peru's capital this week for the OAS's annual meeting.

But inside the Washington-based peace- and democracy-building organisation, their long-running romance has been an open secret, one that made some of its 600 employees feel uncomfortable and intimidated interacting with the boss' alleged paramour, according to a half-dozen individuals including current and former staffers as well as regional diplomats.

Two said they saw the two kissing poolside at the OAS General Assembly in Medellin, Colombia, in 2019. Another individual described them holding hands at a meeting in his office in the summer of 2020. A former US official said he was told by the OAS chief that the relationship was what prompted his separation from his second wife around the time of his re-election in 2020.

At issue are OAS ethics guidelines that say staff members must not have intimate relationships with colleagues in a way that interferes "with the performance of their duties or to disadvantage others in the workplace". It dictates that a manager must back out of any supervisory role of the other individual or that benefits the person in any way.

The 59-year-old Almagro declined repeated requests from the AP to comment. But an OAS spokesman denied Almagro was ever the woman's supervisor, saying that since 2019 she's worked in the OAS's Secretariat for Strengthening Democracy.