Leaders from around the world send messages of support
Tony Blair has led British condemnation of the Spanish train bombings whilst other world and religious leaders also sent message of support.
The Prime Minister and his Cabinet colleagues were "saddened and shocked" to learn of the attacks as they gathered in Downing Street.
A telegram was also sent by Cardinal Secretary of State Angelo Sodano in the Popeís name to Cardinal Antonio Maria Rouco Varela, archbishop of Madrid.
Pope John Paul II called the attacks abominable. "The Holy Father reiterates his firm and absolute disapproval of such actions that offend God, violate the fundamental right to life and undermine peaceful coexistence," the Vatican said.
"While encouraging the beloved Spanish people to continue with determination and without discouragement on the path of peaceful and serene coexistence, he invokes the protection of Our Lady for all and as a sign of his affection and hope, he imparts on everyone his apostolic blessing" the telegram stated.
Meanwhile Mr Blair told the weekly Cabinet meeting in No10: "This terrible attack underlines the threat that we all continue to face from terrorism in many countries, and why we must all work together internationally to safeguard our peoples against such attacks and defeat terrorism."
The Queen also sent her condolences after learning of the attacks.
In a message to King Juan Carlos, she said: "I was shocked to learn of the tragic loss of life following the explosions this morning in Madrid.
"These attacks of terrorism have struck without discrimination, and have horrified the people of the United Kingdom."
George Bush, the United States president, was one of several leaders who spoke by telephone to JosÈ Maria Aznar, the Spanish prime minister.
Meanwhile, dozens of other world leaders sent letters of condolence.
"I appreciate so very much the Spanish governmentís fight against terror, their resolute stand against terrorist organisations like ETA, and the United States stands with them," Mr Bush later told reporters.
Kofi Annan, the United Nationsí secretary general, also sent condolences to the king, expressing the hope that "the perpetrators will be brought to justice swiftly".
The UN Security Council adopted unanimously a resolution which condemned the attacks.
The council said it regarded the attacks "like any act of terrorism, as a threat to peace and security" and expressed "its reinforced determination to combat all forms of terrorism".
Mr Annan said he learned of the attacks "with profound shock and indignation".
"Once again, we see senseless killing of innocent people. The killing of innocent people cannot be justified, regardless of the cause," he said.
Following a minuteís silence at the European parliament in Strasbourg, its president, Pat Cox, said: "There is a general election due in Spain on Sunday. What happened today is a declaration of war on democracy.
"Let Sunday show that Spanish democracy is determined to overcome terrorism."
Romano Prodi, the European Commission president, called the attacks "ferocious and senseless".
"This is not a political act, it is a criminal act against defenceless people... a perverse act of terrorists," Mr Prodi said.
Vladimir Putin, the Russian president, said: "This senseless, barbaric action has again shown that the world community must even more resolutely combat terrorism. Today, as never before, the entire civilised world must unite in the fight against this evil."
The Italian president, Carlo Azeglio Ciampi, denounced the attacks as "abominable violence that wounds every principle of civil existence", but said that they would promote European unity against terrorism.
In Berlin, the chancellor, Gerhard Schrˆder, said that he was "deeply dismayed by this inhuman attack".
Jacques Chirac, the French president, wrote in a letter to Mr Aznar: "In these horrifying circumstances, I extend in my name, and in the name of the French people, my most sincere condolences."
Condemnation of the bombings came from every corner of the globe. The Japanese foreign minister, Yoriko Kawaguchi, called the attacks "unforgivable", while in Chile, Ricardo Lagos, the president, predicted that Spainís population would prove resilient to the horror.
"Our Spanish friends will react the way they know - with the unity of the people. We should not let ourselves be intimidated," Mr Lagos said.
The head of Interpol urged the world to "redouble" its efforts in the fight againstterrorism. Ronald Noble, the international police agencyís secretary general, said: "Since 11 September 2001, Interpol has underlined that the global fight against terrorism is not only against al-Qaeda."