Jihad Ahmed Mustafa Diyab was held in extrajudicial detention for 12 years in Guantanamo. After his release in 2014, he was arrested by Venezuelan security forces and since then has been held incommunicado.
A former Guantanamo prisoner who was relocated to Uruguay nearly two years ago is being held by Venezuela's intelligence agency after travelling to Caracas to reunite with family.
Jihad Ahmed Mustafa Diyab, who was held for 12 years in Guantanamo without being charged, has been unable to communicate with the outside world since he arrived in Caracas on July 26.
His lawyer Jon Eisenberg said Venezuela has ignored his requests to speak to his client by phone.
"I have not been able to make contact with him and have gotten no official response from the Venezuela government as to why he is being detained or where," Eisenberg said in an email to AFP.
"I am currently attempting to find an attorney in Caracas who has experience with the Venezuelan legal system... and can assist in the effort to make contact with Diyab," he said.
Diyab was one of the longest Guantanamo hunger strikers. There were fears that he would die in custody when his weight dropped to dangerously low levels.
The Syrian national, was transferred to Guantanamo after being captured in 2002 near the border region of Afghanistan and Pakistan. He was released to Uruguay in 2014 as part of an arrangement to reduce the number of detainees at the US military prison.
A letter written in July by a group of US Senators, described him as a "weapons smuggler".
Eisenberg represented Diyab in a court challenge to a US Defense Department policy of force-feeding Guantanamo prisoners that went on hunger strike.
He stopped representing Diyab after he was released from Guantanamo but has been advising him regarding ongoing efforts to secure the public release of videos showing him being violently force-fed while he was being held in the US-run offshore prison camp in Cuba.
Diyab had asked the Uruguayan consulate to help him travel to Turkey where he was to meet with his family, Eisenberg said.
One of the six Guantanamo detainees released and resettled in Uruguay as part of US President Barack Obama's effort to fulfill a long-delayed promise to close the infamous prison, neither Diyab nor his counterparts -- including four Syrians, a Palestinian and a Tunisian -- were ever charged or tried.
Although they had been cleared for release, they could not be sent to their home countries because of unrest there.
Venezuela's government has been harshly critical of US treatment of Guantanamo prisoners. The country's late former president Hugo Chavez said in 2009 that Venezuela would be willing to receive Guantanamo prisoners as part of efforts to help close the prison.