Ambulances carry the dead and wounded from some of Madrid's busiest train stations. As many as 10 bombs exploded in the city in what appear to be closely coordinated terrorist attacks.

Addressing the nation, Spanish Prime Minister Jose Maria Aznar called it mass murder, blaming the Basque separatist group ETA and vowing to track down those responsible for what British Foreign Secretary Jack Straw calls a shocking, unbelievable outrage.

"This is, without any question, at least the worst terrorist outrage, which has taken place within Europe since the Lockerbie bombings at the end of the 1980s," he said.

Police later said they had found a van containing detonators along with an Arabic language tape with verses from the Koran. And, an Arabic-language newspaper in London says it has received a claim of responsibility from a Middle Eastern group taking credit for the blast in the name of al-Qaida. All of this has prompted Spanish authorities to now expand their investigation into groups beyond Basque separatists.

Condemnation and condolences were quick from world leaders including President Bush who telephoned King Juan Carlos and Prime Minister Aznar to express his deepest sympathies for the loss of life.

"I told him we weep with the families. We stand strong with the people of Spain. I appreciate very much the Spanish government's fight against terror," he said.

Spain is a close American ally and part of the U.S.-led military coalition that invaded Iraq last year, another indication, according to terrorism experts like M.J. Gohel of the Asia Pacific Foundation, that Thursday's bombings could be a counter attack to the U.S.-led war on terror.

"Spain has been a major partner in the war on terrorism," he said. "Spain has also been involved in the war in Iraq as a major coalition partner. Spain was very much a number two target on the list for al-Qaida."