The Swiss-run International Committee of the Red Cross (ICRC) has reminded the international community of the ban on torture of any kind.
The head of the ICRC, Jakob Kellenberger, told the United Nations Commission on Human Rights that there was no justification for torture, not even for reasons of security.
Addressing the commission during its annual meeting in Geneva, Kellenberger said the "ban on torture and other forms of cruel or inhumane treatment, physical or mental, under any circumstances, is absolute".
He added that he was concerned that there was growing acceptance in some quarters that individuals accused of "horrible acts" did not merit humane treatment. He stressed that "nobody was above the law".
Kellenberger's statement comes one month after a meeting with President Bush in Washington where he raised concerns about detainees at the United States naval base at Guantanamo Bay.
A leaked ICRC memorandum last November accused the US military of using tactics "tantamount to torture" on inmates held at the base.
Many of those held at the base in Cuba are suspected Taliban and al-Qaeda militants who the US says are not legally entitled to rights accorded to prisoners of war.
One year ago the ICRC completed a report on conditions at US prisons in Iraq, which fuelled international outrage over abuse of detainees.
Kellenberger said that prisoners must be treated "humanely and with respect" and that it was the duty of states to ensure that they did not "disappear".
Over the next six weeks, the UN Commission on Human Rights will focus its debate on terrorism, and is expected to agree on a resolution on the issue.
swissinfo with agencies
The ICRC works mainly to protect the victims of conflict by providing humanitarian assistance and conducting prisoner of war visits.
It monitors compliance of the Geneva Conventions, which outline the rules of law in times of war and occupation, including the treatment of PoWs.
The ICRC visited more than 570,000 prisoners detained in 80 countries last year.
Switzerland is the depository state of the Geneva Conventions.