More than a dozen Venezuelans have joined a hunger strike initiated by two of the country’s most vocal political prisoners. Leopoldo López and Daniel Ceballos, staunch opponents of President Nicolás Maduro’s administration, reportedly began refusing food nearly two weeks ago, prompting concern from the United Nations' human rights body Wednesday.

Several student activists and prisoners are participating in the hunger strike in solidarity with López and Ceballos, reported Venezuela’s El Nacional newspaper. Five of the participants are students from the northeastern state of Monagas, while another seven are youths in Caracas who have been occupying the front doors of a church for five days. Two prisoners in a penitentiary in the northern Carabobo state also joined the hunger strike last week.

Ceballos and López began the strike more than a week and a half ago, according to a video leaked from López’s jail cell May 24. In the video, López said he and Ceballos were fighting against “the permanent violations of our rights and to our families.” The announcement followed news that Ceballos had been transferred to a civilian prison outside the capital, away from the military prison where he had been held for the past year.  

Ceballos is on the 12th day of his hunger strike, while López is on his 10th. Both men have been imprisoned for more than a year and face charges relating to their support of last year’s antigovernment protests that resulted in more than 40 deaths. The two Carabobo prisoners, Alexander Tirado and Raúl Baduel, are also serving sentences for their participation in last year’s demonstrations.

The United Nations expressed concern about both prisoners in a statement Wednesday. “We are very worried about detention conditions and the deterioration in health” of Ceballos, Rupert Colville, a spokesman for the UN human rights commission said in a statement Wednesday. “We urge the authorities to guarantee that all detainees on hunger strike have access to medical attention with a doctor of their choosing.”

Alberto Maldonado, a member of the opposition Popular Will party and mayor of the western city of Torbes, told El Nacional Wednesday that Ceballos’ health was frail. “Daniel has lost more than 12 kilos [26 pounds]. He could go catatonic at any moment and die,” he said.

López, meanwhile, is still facing trial, although paramedics and firefighters with oxygen tanks were reportedly present in the courtroom in case he had any health emergencies during the hearing. López is “very thin” but has remained steadfast in committing to the strike, taking in only liquids and essential nutrients, his lawyer told the Associated Press.

Venezuela’s public defender, Tarek William Saab, told TV network Globovisión Monday the government has been “vigilant” in monitoring Ceballos’ and López's health and requesting frequent medical evaluations.