SYDNEY (AFP) - An Australian is being held on terrorism-related charges in Saudi Arabia, officials revealed on Thursday, with the man's brother claiming he has been tortured.

Shayden Thorne, 25, has been held in a jail outside Riyadh for almost 18 months, reportedly after a laptop, which his family says he borrowed from a mosque, was allegedly found to have terrorist material on it.

A spokeswoman for Foreign Minister Bob Carr confirmed his detention and urged a speedy resolution to the case.

"We know that he has been charged with terrorism-related offences, but that is all we've been informed of at this stage," the spokeswoman told AFP.

She added that Mr Carr raised the matter with officials during a visit to Riyadh in June last year and the man had been allowed consular access.

"The minister requested then that the case be finalised in a timely manner and we're still hoping that this will happen," she said.

The Australian Broadcasting Corporation said the man's 23-year-old brother, Junaid Muhammed Thorne, was also jailed for several months after protesting against his brother's arrest, before being released.

It reported that his passport has been confiscated by Saudi authorities and he was in hiding.

Junaid said Shayden, who is originally from Perth but has been living in Saudi Arabia for a decade, had been tortured in prison.

"When he managed to see his lawyer, he told him that, yes, he was beaten very badly, that he was lashed with cables - many, many sorts of torture was exercised on him," Junaid told the broadcaster from Saudi Arabia.

"They took a very, very long time to charge him," he added.

"I mean, he stayed for a year-and-a-half, a total of 18 months without any charges. And then suddenly out of the blue came, I think, six to seven terrorist charges, which is very, very weird, with no proof at all."

Their mother, who lives in Perth but did not want to be named, said Australia was not doing enough to get her sons home.

"Let them go, let them come back," she told ABC.

"If they've got evidence against them OK, fine, but there's nothing.

"I just think that they (Canberra) are not doing as much as what they should be doing to get my boys home."