Human rights advocates gathered September 22 outside the U.N. headquarters in New York City to protest the detainment of two Iranian physicians, who have been held in a high-security prison in Tehran since late June, The Washington Post reports.

It is believed that the brothers, Arash and Kamiar Alaei—who have led Iran’s successful strategy of focusing on drug addicts in order to halt the spread of HIV/AIDS—were arrested and charged with attempting to recruit and train people to topple the Iranian government.

“They have been involved in organizing gatherings on topics such as AIDS that have received attention from domestic and international NGOs,” said Hasan Hadad, the deputy general prosecutor of Tehran. “They acted to recruit individuals to travel abroad with the aim of training them on overthrowing the system. They were well-aware of their activities and topics of training, such as velvet revolutions.”

According to the article, 3,200 AIDS researchers, public health activists and colleagues have signed a petition for the Alaeis’ release. Many human rights advocates worry about the brother’s fate, especially since the country’s number of executions has increased greatly since Mahmoud Ahmadinejad became Iran’s president.