Amnesty International is calling for the release of 35 men it says are being held illegally and without charge by South Sudan's National Security Service.

The group said Friday that the detained men include a journalist and a dean at the University of Juba.

It said that none of the detainees has had access to a lawyer, while some have been beaten during interrogations in what could amount to torture.

The rights group says 35 men represent "just a small fraction" of individuals who have been arbitrarily detained by the government.

South Sudan, which erupted into violence in December 2013, is awaiting the return of rebel leader Riek Machar, who will take up the post of vice president under the terms of a peace deal signed last year.