Madrid - Spanish officials, stunned by co-ordinated bomb blasts in Madrid on Thursday that killed 192 people and wounded more than 1 400, said they were keeping their lines of investigation open after clues emerged possibly implicating Basque or Islamic militants.
The atrocity, which Spanish media and officials described as "our own September 11", came exactly two and a half years after the attacks in New York and Washington, or 911 days, and just three days before general elections that the ruling conservative Popular Party is widely expected to win.
The carnage, carried out in four trains and three railway stations in the southeast of the capital in morning rush-hour, was the worst terror attack in Europe since the 1988 Lockerbie bombing that killed 270 people.
Spanish King Juan Carlos said in a televised address to the people after visiting survivors in one of the city's hospitals, "A nightmare has struck showing terrorism's cruel face."
"Your king is suffering with all of you and shares your indignation."
The news of possible al-Qaeda involvement sent stock markets and the US dollar plummeting.
The Dow Jones index in New York slid more than one percent, following European indices down. The dollar weakened against the euro, which went from 1.2222 dollars late on Wednesday to 1.2352 on Thursday.