HOPES for an Australian university graduate being released from "terrible conditions" in a South Sudan jail have been dashed after it was revealed he has been charged with harbouring a murder suspect.

However, family members of Manyang Maker Tulba , 22, say the charges are "outrageous" and have been trumped up by South Sudanese authorities to cover up his unlawful imprisonment.

Mr Tulba, an Australian citizen who was born in South Sudan but has lived in Perth since 2003, has been held in a military prison in Rumbek, in the country's north, since February as part of a state investigation into violent ethnic clashes which left six people dead and four injured.

Older brother Makur Maker and cousin Adhiel Malual, both of Perth, said Mr Tulba - along with his mother and father - had been jailed without charge and tortured with daily beatings and whippings and starved of food and water during his time in prison.

Yesterday, a spokesperson for Foreign Affairs Minister Bob Carr confirmed Mr Tulba, who graduated from Perth's Edith Cowan University in 2011 with a bachelor's degree in criminology and justice and was enlisted in the Army Reserve, has now been charged with "screening or harbouring" an alleged murderer.

The spokesperson said two consular officials from the Australian Embassy in Nairobi had visited Mr Tulba on Tuesday and Wednesday and had addressed South Sudan authorities on the case.

Ms Malual said she was "shocked" to hear her cousin had been charged.

"It's not fair and I'm really disappointed and shocked," she said.

"It's just ridiculous, they're just trying to cover their backsides because they've been holding him for so long and torturing him, and they have to find something to keep him in jail.

"It's just really outrageous."

Ms Malual said her family was extremely worried for Mr Tulba's welfare and had been frustrated by the slowness of Australian authorities.

"It seems authorities have moved very slow, it's too slow, but I hope they're going to do whatever they can to just make the situation better," she said.

"I'm hopeful the Australian government can do something and get him out of there and bring him home because this is his home and he belongs here.

"He's an Australian citizen and he's lived here almost all his life and he's worked hard, he's a part of this country and he even had plans to join the army and fight for this country, so this is a bit frustrating that it's too slow."

Ms Malual said Mr Tulba's sister, who has been bringing him food in jail but has not been allowed to actually meet with him, had told family members he was being kept in "terrible" conditions.

"The whole family is really unstable still, just not knowing what's going to happen," Ms Malual said.

"We're just trying our best to stay strong because he does actually need our support.

"I am really hopeful (he will be released), it will be very disappointing to the family if (the government) told us that they can't do anything."

She said Mr Tulba had plans to get married in Rumbek and return to Perth to start a family and undertake his masters degree when he was arrested last month.