The report titled Human Rights Ignored in the War on Terror, which accuses Pakistan, a major US ally, of systematically committing human rights abuses against Pakistani and foreign suspects.
Pakistan's routine practice of offering rewards running to thousands of dollars for unidentified terror suspects has led to illegal detentions of innocent people, said Claudio Cordone, senior director of research at Amnesty International.
"Bounty hunters [including police officers and local people] have captured individuals of different nationalities, often apparently at random, and sold them into US custody," he said.
Pakistani government officials could not immediately be reached for comment.
The Amnesty allegations come days after the country's president, Geneneral Pervez Musharraf, revealed in his memoir, In The Line of Fire, that Pakistan captured 689 al-Qaida terror suspects, and turned over 369 to Washington.
Without specifying how much was paid, Musharraf said: "We have earned bounties totaling millions of dollars."
"The road to Guantanamo very literally starts in Pakistan"
Claudio Cordone, senior director of research, Amnesty International
Cordone said that many detainees ended up in secret locations or at the US prisons, including Guantanamo Bay and Bagram, north of Kabul.
Cordone said: "Hundreds of people have been picked up in mass arrests, many have been sold to the USA as 'terrorists' simply on the word of their captor, and hundreds have been transferred to Guantanamo Bay, Bagram Air base or secret detention centers run by the USA.
"The road to Guantanamo very literally starts in Pakistan."
In a statement, Amnesty has said the increase of enforced disappearances and holding of suspects incommunicado puts such detainees at risk of torture and unlawful transfer to third countries.