The London-based Al-Quds al-Arabi said on its Web site that it had received a statement from "The Brigade of Abu Hafs al-Masri (al Qaeda)" in which the group reiterated its claim of responsibility for the March 11 attacks that killed more than 200 people and wounded 1,600.
"Our brigades are getting ready now for the coming strike," said the statement dated March 15. "Whose turn will it be next? Is it Japan, America, Italy, Britain, Saudi Arabia or Australia?"
The statement warned these countries that "the brigades of death are at your doors," adding that they would strike "with an iron hand at the right time and place."
The United States believes the Abu Hafs group lacks credibility and has only tenuous ties to al Qaeda. In the past, the group has claimed responsibility for events to which they were not connected — such as last summer's blackouts in North America and Britain.
The group also reiterated its claim of responsibility for the bombing of the U.N. headquarters in Baghdad last August which killed 22 people, including the world body's chief envoy to Iraq, Sergio Vieira de Mello.
The statement described the United Nations as "America's tail."
"The crimes of the United Nations against Islam are countless. The way to get rid of that humiliation is through holy war that will continue until doomsday," the statement said.
The Web site did not say how the statement had been received. But Al-Quds al-Arabi has received e-mails from this group in the past. On the evening of the Madrid bombings, the paper released a copy of an e-mail from Abu Hafs al-Masri in which they made the first claim of responsibility.
Spanish authorities suspect an al Qaeda-linked cell carried out the. Moroccan authorities have said the emerging evidence in the Madrid attacks points toward Ansar al-Islam, a guerrilla group blamed for terrorist strikes in Iraq, Jordan, Turkey and Morocco. Other groups believed to be involved in the bombings are Salafia Jihadia and Moroccan Islamic Combatant Group.
The Spanish legislator Gustavo de Aristegui, spokesman for the Popular Party which was defeated in Sunday's elections, has cast doubt on Abu Hafs al-Masri's claims.
"They are not capable of committing these attacks, much less of declaring a truce," he told The Associated Press in Madrid.
A telephone salesman from Morocco, Jamal Zougam, is emerging as the key suspect in the Madrid bombings. He was arrested two days after the attacks.
Spanish police have been interrogating two other Moroccans, including Zougam's half-brother, and two Indian men.
Since last week's deadly bombing, countries around the world have been on heightened alert.
In the claim of responsibility for last week's bombing, the al-Masri group said "the strike of the black wind of death, the expected strike against America, is now at its final stage — 90 percent ready — and it is coming soon, by God's will."
Japan toughened its guard against terrorism on Thursday, boosting police agents at major railway stations in Tokyo. Japan's conservative government, a firm supporter of the U.S.-led invasion of Iraq, has insisted the Madrid bombings would not shake its resolve to back Washington.
"Terrorist groups want to create confusion and make people worried, but we should not be swayed," Prime Minister Junichiro Koizumi said.
The government of Spanish Prime Minister Jose Maria Aznar, which supported the war, was ousted in an election three days after the bombings. Spain's newly elected Socialist prime minister has said he will pull 1,300 troops from southernunless the United Nations takes control of peacekeeping — a promise he made before the bombings.
The Bush administration has been trying to steel the nerves of other countries where anti-war sentiment runs high.
"It is the wrong message to let terrorists think that they can influence policy, that they can influence elections," presidential press secretary Scott McClellan said.
From Australia to Poland, countries with troops in Iraq fear they could be the next terrorist target, and the Bush administration acknowledged that U.S. allies could pay a price.
"Any country that allies itself with the United States, unfortunately, is a target," John Pistole, the FBI's executive assistant director for counterterrorism, told Sydney's 2UE radio station.
Australia's foreign minister promised that the government would not back away from the alliance. London's police chief and mayor warned that an attack might be inevitable. In South Korea, the acting leader called a meeting of senior officials to review anti-terrorism efforts, saying the country is a possible terrorist target.
NATO allies on Tuesday agreed to widen their anti-terrorist naval patrols to the entire Mediterranean Sea as they began analyzing a Greek request for increased protection for this summer's.
Even some countries that opposed the war were on guard. The leaders of France and Germany said Tuesday that the deadly train bombings in Madrid underscore Europe's need for a joint plan to fight terrorism.
"All of Europe is the theater for terrorist actions," German Chancellor Gerhard Schroeder said. "So we must, together, as Europeans, confront this terrorism."
French officials announced Tuesday they are investigating threats issued by a radical Islamic group against France and its overseas interests.