Human Rights Watch urged Prime Minister Awn Khaswaneh on Wednesday to probe the death in custody of a 20-year-old Jordanian man, who allegedly helped two Syrians buy arms.
It called for an "independent inquiry into the death of Najem Zubi ... when in detention at the military intelligence offices in Amman, on 16 November, 2011," in a letter to the prime minister.
"To date, we are not aware of any investigation being launched into the case by a military prosecutor," said the letter from Christoph Wilcke, a HRW senior researcher.
Wilcke added that even if the military were to investigate, HRW would continue to urge an independent inquiry "since military justice in Jordan lacks the requisite measure of independence."
Jordanian officials have said Zubi, a taxi driver from the northern town of Ramtha, was arrested along with two Syrians whom he took to an arms dealer, adding that he "hanged himself with his bedding" while in detention.
His death sparked violent reaction from his relatives, who belong to one of the largest tribes in northern Jordan. Accusing the authorities of killing the man, his family blocked a road to neighbouring Syria after setting fire to the governor's offices, the courthouse and a police car.
Residents of Ramtha, which lies across the border from the restive Syrian city of Daraa, often smuggle clothes, food and other goods across the frontier.
But border controls have been stepped up since the outbreak of a deadly anti-regime revolt in Syria in March.