An audio tape purportedly from top al Qaeda official Ayman al-Zawahri warned the United States on Sunday it would pay a high price if it harmed detainees at a US base in Cuba, saying the "real battle" had not yet begun.
Washington is holding more than 600 people from 42 nations at a special camp at the Guantanamo Bay naval base. US plans to try six of them in military tribunals that could hand out death sentences have sparked international criticism.
An Arabiya official said the channel believed the voice on the tape was that of Zawahri - considered to be al Qaeda leader Osama bin Laden's right-hand man. It was not clear when the tape was made.
The speaker vowed to avenge every killing and ruling passed against Muslims detained at Guantanamo.
Zawahri has appeared at bin Laden's side in almost every videotaped statement from the al Qaeda leader since the September 11, 2001 attacks.
The speaker threatened to punish any country that hands over any Muslim suspect to Washington.
Zawahri is an Egyptian doctor who set up a militant group that tried to topple Egypt's government in the 1990s.
It was the first audio tape apparently from him since May 21 when another taped message made threats against the United States.
The captives at Guantanamo Bay include nationals from Britain, Australia, Saudi Arabia, Pakistan and Afghanistan but the US military has not given a precise breakdown.
The detainees, suspected members of al Qaeda and others caught in what Bush calls the "war on terrorism," have been held and interrogated without being charged.
Human rights groups have criticized Washington for refusing to give the detainees the rights accorded to prisoners of war under international treaties.
Last month Washington said six suspects, including two Britons and an Australian, could face military trial. It accused them of attending "terrorist" training camps and said they may have been involved in financing al Qaeda.
Bowing to pressure from Britain and Australia, Washington said later it would not seek the death penalty in any military trials held for the nationals of those two countries.