The human rights group on Thursday also blasted the United States for failing to launch an independent investigation into the Abu Ghraib prison scandal, a year after images of abused detainees first shocked the world.
"People around the world will be recalling the horrific images they saw a year ago and wondering what happened to those prisoners," Amnesty secretary-general Irene Khan said, pointing out that only a handful of low-ranking US soldiers had been prosecuted or disciplined over the outrage.
"But what was the role of those higher up, including for example, the US secretary of defence?" she demanded, referring to Donald Rumsfeld.
A year after the scandal broke, only five of seven US guards have been punished.
New torture cases
"The US government must set up an independent inquiry into all aspects of the USA's 'war on terror' detention and interrogation practices," Khan said.
A US probe has cleared Ricardo
Sanchez of any wrongdoing
The senior commander of the US military in Iraq at the time of the scandal, Lieutenant-General Ricardo Sanchez, was cleared on Friday of any wrongdoing by a US military investigation.
Amnesty also said there were new reports of torture carried out by the new, US-trained Iraqi security forces.
In February, three men died in custody after being arrested at a police checkpoint, it said.
The bodies "were found three days later, bearing clear marks of torture from beatings and electric shocks", it said.
The rights group also spoke about cases of torture carried out at Iraq's Interior Ministry and said the US authorities were aware of them.
It cited one former prisoner, Ali Safar al-Bawy - an Iraqi resident in Sweden - describing how he was given an electric shock while held captive for three weeks in July last year. The man also alleged that a child prisoner had been sexually abused by Iraqi guards.
Amnesty called for the anniversary of the publication of the photographs from Abu Ghraib "to be marked by the strongest condemnation of all forms of torture by the US and Iraqi governments".