The Guantanamo Bay prison camp was ordered closed by the US president, in addition a review of the detainees' trials was ordered, along with the closure of CIA secret prisons and an end to harsh interrogations.

But the orders appear to leave loopholes that could allow some controversial US practices to continue.

Extraordinary renditions, where "terror" suspects are apprehended and transferred from countries by US intelligence services or their allies, without going through any legal process, could still be carried out.

A senior Obama administration official has said the policy of extraordinary rendition would continue while a task force headed by the US attorney general investigates the issue.

The task force will report back to Obama in six months.

The official also said the US would not render anyone to a country that tortures and will gain assurances from the countries that they do send people to that the suspects won’t be tortured.

Michael Scheuer, a former CIA agent who was head of the organisation's Bin Laden Unit in the 1990's, told Al Jazeera it was not clear what would now happen to suspects detained as part of the rendition process after the secret prisons had been closed and other countries off-limits due to torture claims.

"I don't know where they would be taken ... but they wouldn't be brought here [to the US]," says Scheuer.

"Most of those detained have been arrested by foreign intelligence agencies so a US court could not be sure they hadn't been roughed up at all and that documents had not been tampered with."

- 'Black sites'

Extraordinary renditions became best known as part of the Bush administration's so-called war on terror begun following the September 11 attacks on New York.

But the practice had originally been authorised by Bill Clinton, the former US president, in the mid-1990s, to target al-Qaeda units without using the legal process.

It is not known how many people have been subjected to rendition by US intelligence agencies or their allies, but the number is believed to have increased substantially following the beginning of the "war on terror".

Many of the detainees are said to have been held at facilities in Egypt and Jordan, key US allies in the Middle East, or at secret prisons, (so-called "black sites") in Europe or elsewhere.

A Council of Europe investigation into the use of rendition in 2006 found that more than 100 people had been detained as part of the US rendition program.

- Abuse claims

Khaled al-Masri says he was abused in an
Afghan prison [AFP]
Khaled al-Masri, a German citizen of Lebanese descent, says he was abducted in December 2003 at the Serbian-Macedonian border and then flown to a detention centre in Afghanistan, where he was interrogated and abused.

Al-Masri says he was released in Albania in May 2004, and that his captors told him he was seized in a case of mistaken identity.

Twenty-six Americans, nearly all of them believed to be CIA agents, are being tried in absentia in Italy on charges of kidnapping an Egyptian-born imam in 2003.

Prosecutors there say a CIA-led team kidnapped Hassan Mustafa Osama Nasr from the streets of Milan and secretly flew him to Egypt.

Nasr says he was tortured under questioning there and held without charge before being released in 2007.

- Guantanamo concerns

Concerns have been raised about other elements of the executive orders on security Obama signed on Thursday.

The Center for Constitutional Rights, a US rights group, issued a statement on Thursday warning Obama against allowing the CIA a new way to use torture, following any reviews of interrogation practices.

But others believe that the Obama administration is genuinely committed to ending many controversial practices relating to the "war on terror."

Devon Chaffee, an advocacy counsel at Human Rights First which has called for a moratorium on renditions, told Al Jazeera that she believed the "spirit" in which the orders were enacted meant that it was unlikely that abuses would continue.

But Scheuer has also expressed concerns about Obama's executive orders and described the decision to close the Guantanamo Bay prison camp as the act of an "immature president".

He argues that the decision to close Guantanamo and possibly free detainees could endanger US national security by allowing freed al-Qaeda members to plan more attacks.

A report in the New York Times newspaper published on Friday alleged that a former Guantanamo inmate transferred to Saudi Arabia in 2007 is now the head of the group's Yemeni cell and that he was involved in an attack on the US embassy there in September.

"We have two options," says Sheuer.

"We can shoot them on the battlefield ... or we can treat them as soldiers without uniforms and treat them as prisoners of war and release them when the war is over ... so maybe never," he said.