Juba — The US embassy in South Sudan has demanded the unconditional release of one its nationals, allegedly arrested by the country's National Security Service (NSS).

Elton Mark McCabe, according to the embassy, was "arbitrarily" arrested in Juba, the South Sudan capital and has now been transferred from NSS detention center to Juba Central Prison.

The trial of McCabe, who has reportedly obtained a legal counsel and been granted access to medication, is due on 22 November. McCabe, was arrested on October 14.

In a statement, his wife, Anne McCabe, said NSS agents abducted him and Mohamed Oglah, an Iraqi national over allegations of attempted kidnap. McCabe, according to his wife, came to Juba this year after Oglah invited him to an investment conference in Juba, The two, she said, had previously worked together in Iraq.

It is widely believed that McCabe was working in South Sudan as a construction contractor, with a private company.

"We have raised his case at the highest levels of South Sudanese government, urging that he be granted due process as stipulated in South Sudan's Transitional Constitution," the embassy said in a statement to Sudan Tribune.

The embassy, in the statement, also expressed concern over reports of "arbitrary" arrest and detention in general in South Sudan, urging the country's government to ensure the detained US citizen gets a fair trial.

It remains unclear why McCabe is under detention and NSS authorities have been silent over the matter.