Saudi Arabia has voiced "deep indignation" at reports that a copy of the Koran was desecrated at the US prison at Guantanamo Bay in Cuba.
More than 500 inmates are being held at Guantanamo Bay
Riyadh called for a quick investigation into the alleged incident and for the perpetrators to be punished.
It is the first Arab state to comment officially on the reports. Reaction in the Arab world has been muted.
On Thursday the US secretary of state promised prompt action if allegations of desecration prove true.
At least seven people have died in Afghanistan in anti-American protests sparked by the reports.
But Condoleezza Rice appealed to Muslims to resist calls for violence.
The US authorities say they are investigating the allegations.
But head of the US Joint Chiefs of Staff, General Richard Myers, told a Pentagon press conference that investigations so far had not turned up any evidence to back the claims.
Close US ally
"The government of Saudi Arabia is closely following, with indignation, media reports of desecration of the holy Koran at Guantanamo," a statement carried by the official news agency said.
Saudi Arabia "appeals to the concerned American authorities to carry out a quick investigation in the matter".
Riyadh "stresses that in case the reports were true, deterrent measures should be taken against those perpetrators to prevent its recurrence and to protect the sentiments of Muslims all over the world".
Anti-American protests in Kabul have targeted western agencies
Saudi Arabia is a close US ally. It is also home of Islam's two holiest sites, Mecca and Medina in western Saudi Arabia, and sees itself as a leader of Muslims around the world.
Ms Rice said desecration was abhorrent and disrespect for the Koran would not be tolerated.
She urged Muslims in America and throughout the world to stop the violence.
"I am asking that all our friends around the world reject incitement to violence by those who would mischaracterise our intentions," she said.
"Disrespect for the holy Koran is not now, nor has it ever been, nor will it ever be, tolerated by the United States," she said.
Newsweek magazine first reported that interrogators at the US Guantanamo Bay prison had flushed at least one copy of the Koran down a toilet.
The US is holding about 520 inmates at Guantanamo Bay, many of them al-Qaeda and Taleban suspects captured in Pakistan and Afghanistan following the 11 September 2001 attacks in the US and subsequent US-led invasion of Afghanistan.