A Cuban LGBT rights activist says authorities on Monday prevented him from leaving the country.

Nelson Gandulla Díaz, president of the Cuban Foundation for LGBTI Rights, told the Washington Blade that his Copa Airlines flight to Panama City’s Tocumen International Airport was scheduled to depart from Havana’s José Martí International Airport at 7:50 a.m. Gandulla was to have then flown from Panama City to the Colombian city of Cartagena in order to attend a workshop organized by Caribe Afirmativo, an LGBT advocacy group.

He was to have returned to Cuba on Jan. 17.

Gandulla told the Blade during a telephone interview from Havana that he was waiting to pass through immigration at José Martí International Airport at around 5:40 a.m. when security agents “pulled me out of the line.”

“They told me that I was unable to leave the country,” he said.

Two other independent Cuban LGBT rights activists were also traveling to Colombia to attend the same Caribe Afirmativo workshop. Gandulla told the Blade they were able to leave Cuba “with no problem.”

Incident ‘is a violation’

Gandulla and other members of the Cuban Foundation of LGBTI Rights are vocal critics of the Communist island’s government. They also frequently criticize Mariela Castro, the daughter of Cuban President Raúl Castro who promotes LGBT-specific issues in the country as director of the National Center for Sexual Education.

Gandulla said security agents interrogated him in the city of Cienfuegos for more than two hours on Dec. 10 about his work with Caribe Afirmativo. He told the Blade they threatened to arrest him and told him he was not allowed to leave Cuba.

Gandulla told the Blade on Monday that one of the security agents who interrogated him last month came to his home near Cienfuegos over the weekend.

He was in Havana at the time, but he told the Blade he expects the security agent will return once he is back in the city. Caribe Afirmativo Director Wilson Castañeda said immigration officials in Cienfuegos have summoned Gandulla to their office.

“It is a violation,” Gandulla told the Blade.

Gandulla said a police officer came to his home last March before President Obama’s historic trip to Cuba and asked him whether he planned to leave the province of Cienfuegos.

Authorities at José Martí International Airport in July 2015 detained Gandulla and the two activists with whom he was to have attended the Caribe Afirmativo workshop for several hours when they tried to re-enter Cuba. Gandulla told the Blade they searched their luggage and confiscated their cameras and USB drives for 30 days.

Security agents were reportedly near Gandulla’s home in May 2015 when the Cuban Foundation for LGBTI Rights honored the Blade for its coverage of the country’s LGBT rights movement. Gandulla’s colleagues and other independent LGBT rights advocates have said authorities have detained them, harassed them and confiscated their cell phones because they publicly criticize the government.

The Cuban government has not returned the Blade’s request for comment.