Hearings began Thursday for six Algerians who are fighting their detention at Guantanamo Bay -- the first such challenge in a federal court since the war-on-terror US prison opened in 2002.

The six, who were seized in Bosnia, remained in the Guantanamo Bay, Cuba US naval facility Thursday but were linked into the Washington court hearing by telephone, with the entire proceeding translated for them.

Theirs is the first such case to go to trial since the US Supreme Court on June 12 granted Guantanamo detainees access to the civil court system to challenge their detention on habeas corpus grounds.

`It is not a trial over these men being guilty or innocent, it is only a trial about whether the (US) president can say legally that based on these facts and this law, `I have a basis for holding these men`,` defense lawyer Robert Kirsch told AFP earlier.

Federal judge Richard Leon spent much of the first morning of the hearing detailing to the six men the conditions by which they can take part in the process, which is expected to take about one week.

He explained that, because their cases heavily involved evidence the government classifies as secrets, most of the hearings would involve just himself and the lawyers for the government and the detainees, and be closed off to observers and detainees.

`Detainees received an unprecedented due process in these proceedings,` he assured, repeatedly reminding that the case was unprecedented in US law.

The two sides briefly delivered the arguments which they will be able to further develop in public.

Government attorneys said they would provide proof that at the time they were arrested in October 2001, the six men had planned to travel to Al-Qaeda camps in Afghanistan.

The defense rejected that argument, saying the six were arrested by `mistake.`

The judge is expected to announce his decision in about 10 days.