The bombing attacks in London on Thursday brought widespread condemnation from other countries and statements of solidarity with the British people, while many governments raised terror alert levels and stepped up vigilance on transportation systems.
In Spain, where last year's terrorist attack on Madrid commuter trains was fresh in people's minds, Prime Minister Jose Luis Rodriguez Zapatero placed the country on a maximum security alert.
"Above all, I want to express my most absolute condemnation -- the condemnation of the government and of the Spanish people -- for these brutal actions," Zapatero said at a news conference.
"Spain has suffered the blight of terrorism for decades and was victim on March 11 last year of the most horrific attack on record until then in Europe," he added. "Spaniards are very familiar with the suffering the British people are experiencing today. We are fully united in their pain, just as they, and so many other world communities, joined in ours on other occasions."
After meetings with cabinet members, Zapatero ordered an alert that mobilized police and the national Civil Guard as well as the nation's armed forces. The alert system was established after the March 11, 2004, attacks on commuter trains in Madrid, in which 191 people died and more than 1,800 were injured. Security was stepped up at strategic targets, including transportation, utilities, department stores and sports arenas.
"When these things happen, every victim of terrorism -- especially victims of bombs or explosions -- experiences renewed feelings," said Cristina Salado, a spokeswoman for the Association of March 11 Victims. "For those affected by March 11, the reaction was probably even stronger, considering it was so much more recent."
Salado, who was wounded in a 1985 Islamic terrorist attack in Spain that killed her husband, said she was horrified when she saw the news from London. "I felt and remembered what it is like to be in a situation like that. I thought about what the people trapped on the trains were feeling and what their families were feeling."
Throughout Europe, officials tightened security as they condemned terrorism.
Authorities in Berlin, Moscow and Paris increased security on their subway systems. Many governments also elevated terror alerts and asked transportation workers to be vigilant and look for suspicious objects.
Call centers in India, which handle many of Britain's National Rail telephone inquiries, said the number of calls doubled after the bombings. Officials said they brought in extra employees and asked some to work overtime.
European Union legislators called on members of the 25-nation organization to boost cooperation against terrorism and offered to help Britain coordinate its emergency response to the bombings. The bombers struck "at the very heart of Europe," said the E.U.'s justice and security commissioner, Franco Frattini.
Leaders of the Group of Eight countries meeting in Scotland called for unity and condemned the attacks.
"Terrorism will not prevail if we stand united with determination," Italian Prime Minister Silvio Berlusconi said. German Chancellor Gerhard Schroeder said nations must fight terrorism "with all the means at our disposal."
In response to the London attacks, Secretary of State Condoleezza Rice ordered U.S. embassies around the world to review their security arrangements. The State Department set up a task force to deal with the London bombings and to coordinate queries and information about Americans in Britain. By noon, the task force had received more than 17,500 inquiries about U.S. citizens who might have been affected by the attacks, State Department spokesman Sean McCormack said. But the State Department said it had nothing to indicate that Americans were among the injured or dead.
In an interview with the BBC, Rice said the London bombings illustrated why nations must go "on the offense" to defeat terrorism.
"That's why you have to take away territory from places like Afghanistan. That's why you have to fight in the mountains of Pakistan. That's why it's important to have new and stable democracies in the Middle East in places like Lebanon or Iraq," Rice said.
In Pakistan, a key U.S. ally in the war on terrorism, the president, Gen. Pervez Musharraf, said it was "imperative that we stand together . . . to eliminate this menace."
Iraqi Prime Minister Ibrahim Jafari sent Blair a message saying the attacks had no "relation to religions and human morals."
"While I am expressing my deep sorrow to you and, through you, to the British people and families of victims, I confirm to you our deep will to rid the evil of terrorism in any country as it appears," the message said.
Staff writer Robin Wright in Washington contributed to this report.