Lawyers have filed petitions in a US court on behalf of nine prisoners from the Guantanamo Bay detention centre.
The US has been setting up an annual review process for inmates
The petitions are the first to be filed since a US Supreme Court ruling earlier this week said they could challenge their detention in US courts.
The Center for Constitutional Rights, which is part of the legal action, says the petitions concern nine detainees out of nearly 600 still at Guantanamo.
The petitions say the detention is illegal and demand the men's release.
The detainees named include two Britons, Moazzem Begg from Birmingham and Feroz Abbasi from Croydon in London, three French citizens and a Turk, two Arabs from Jordan and Iraq and a Canadian.
The petitions come hours after the Bush administration said it might release some of the prisoners.
BBC Pentagon correspondent Nick Childs says it is increasingly clear that the administration was caught off-guard by Monday's ruling.
By a margin of six to three, the court decided that the nearly 600 prisoners being held at Guantanamo Bay did have a legal right to challenge their captivity.
The ruling passes no judgement on the guilt or innocence of those being held.
Moazzem Begg's father Azmat welcomed the news, saying he was very worried about his son's wellbeing after two-and-a-half years in detention.
He said: "He should be medically and physically examined and if he has done anything wrong, all right, take him to the court.
"If he has not done anything wrong, he should be released. I do not know why they are keeping him there.
"He must be immediately released and our government should take full useful force to take him back rather than delay it."
The Pentagon spokesman noted that the US has already been setting up an annual review process for the nearly 600 prisoners being held at the US naval base on Cuba.
Under the system - due to begin soon - a panel of three military officers will carry-out case-by-case reviews to determine whether prisoners no longer pose a security threat and can be released.
The Pentagon has already released more than 130 prisoners. But the reviews have been criticised by campaigners because the prisoners will continue to be refused access to lawyers.
The Supreme Court ruling is being seen as the biggest legal setback to President George W Bush since his war on terrorism began following the 11 September 2001 attacks.
Detainees from 40 countries are currently being held at the Cuba base. Most of them were captured in Afghanistan in late 2001 during the US-led invasion to oust the Taleban regime.
Many have spent more than two years in captivity without being charged.