Speaking a day after tens of thousands of Muslims protested against the alleged Quran abuse by American interrogators, visiting US Assistant Secretary of State for South Asia, Christina Rocca, told a Pakistan television network that any mishandling of a holy book was unacceptable.

"It is not just a question for Pakistan. This is a question for the United States, where we have many Muslims," Rocca, who was in Islamabad for talks, told the Geo network on Saturday.

"It is not just a question of the Quran, it's the question of handling of any holy book at all. In the United States, we stand for tolerance, religious tolerance and freedom of worship, and this extends to detainees, all of whom are allowed to worship freely."

Muslims around the world were outraged earlier this month when Newsweek magazine claimed that military interrogators at Guantanamo Bay prison in Cuba placed a Quran in a toilet to induce a prisoner to talk.

Newsweek later retracted the report, but an investigation by US officials has found at least five cases of the Quran being mishandled at Guantanamo since 2002.

However, senior officials said on Thursday that no clear evidence of the alleged toilet incident was found.

They refused to say specifically what kind of mishandling of the Quran was allegedly uncovered, but suggested that it was generally inadvertent.