A letter attributed to an al-Qaida affiliate has claimed responsibility for Thursday's series of explosions in Madrid that killed at least 190 people.
The letter -- sent to the London-based Arabic newspaper al-Quds al-Arabi --says the "death squad" had penetrated what it called "one of the pillars of the crusade alliance -- Spain."
The letter was attributed to the Abu Hafs al-Masri Brigades, which has claimed responsibility for deadly terrorist attacks in the past on behalf of al-Qaida. But its claim of being behind last year's widespread blackout in the United States and Canada proved false.
Thursday's letter could not be independently verified. It also says al-Qaida was behind this week's deadly bombing on a masonic lodge in Turkey.
The Abu Hafs al-Masri Brigades also warned in the letter a major attack on the United States is imminent.
Earlier, Spanish authorities said they discovered a van with detonators and Arabic tapes of readings from the Koran (in the town of Alcala de Henares) near Madrid.
Following the discovery, Interior Minister Angel Acebes told his security forces not to rule out any possible line of investigation.
He previously said he believed the Basque separatist group ETA was behind the blasts, which also wounded more than 12,00 people. The head of the outlawed Basque political party, Batasuna, denied ETA carried out the attack, suggesting "Arab resistance" is responsible for the bombings.
Spanish authorities say at least 10 nearly simultaneous explosions at or near three train stations during the morning rush hour sliced open cars and spread havoc. The blasts came ahead of Sunday's general elections.
Prime Minister Jose Maria Aznar has vowed authorities will bring to justice the terrorists responsible for the attack, which he called a mass murder. He urged Spaniards to join in demonstrations tomorrow (Friday) evening to protest the attacks. He also promised authorities will defeat those responsible and reaffirmed his government's position rejecting any talks with terrorists.
In Washington, U.S. officials say it is too early to conclude who set off the explosions, refusing to exclude the possibility of al-Qaida involvement.
Meanwhile, all campaigning for Spain's election has been called off, and Mr. Aznar has declared three days of mourning for the victims.
Information for this report is provided by AP, AFP and Reuters.