A Spanish judge on Sunday charged two Chechen members of Al-Qaeda with belonging to a terrorist group and possessing bomb-making material, authorities said.
The two men were arrested Wednesday as they headed on a bus for the French border. Another man, a Turk, was arrested in a flat in the southern province of Andalucia, where police discovered the explosives.
Judge Pablo Ruz, who ordered the two Chechens jailed pending trial, based his decisions on information provided by US, French, Russian and Gibraltar authorities.
He said he could see connections between the two Chechens and other people investigated for terrorist group ties.
The two Chechens charged Sunday are Eldar Magomedov, who also goes by the name Ahmad Avar, and Muhamed Ankari Adamov.
According to Spanish court documents, US authorities provided information showing that Magomedov had participated in "terrorist activities" in Waziristan, Pakistan and Afghanistan since 2010.
Russia also supplied "information linking the detainee to terrorist organisations of an international character, locating him from 2010 on Pakistan and Afghanistan territory," said the documents.
The Turkish man was identified as Cengiz Yalcin, who was ordered detained Friday after Spain's interior minister said investigators had evidence suggesting the trio were planning attacks in Europe.
The judge accused Yalcin of "possession of explosive substances and devices with terrorist aims", but did not agree with prosecutors that the man belonged to a terrorist group.
The two Chechens have denied the allegations against them and say they came to Spain to seek asylum.
Yalcin's lawyer said his client was an engineer with an international company who had lived for seven years in Gibraltar and had a British work permit.
After the men were arrested Wednesday, Interior Minister Jorge Fernandez Diaz said investigators had a "clear indication" they had been planning an attack in Spain or elsewhere in Europe.
He called the suspects "extremely dangerous people," including one who was "a very important operative in Al-Qaeda's international structure".
The judge's decision, released Sunday, said video evidence seized from Yalcin could "rationally suggest the preparation" of an attack and that the explosives found in the Turk's home had a "seriously deadly potential."
Given the links between the three men since May, and given that Yalcin had "paid for the travel expenses and journey to Spain" for the two Chechens, the judge decided to also charge the two for possession of explosives.
Authorities have thwarted several suspected jihadi operations in Spain in recent years, especially in the Catalonia and Valencia regions.
On March 11, 2004, bombs exploded on packed commuter trains in Madrid, killing 191 people and wounding 1,841 others in attacks linked to Al-Qaeda.