Two Russians suspected of plotting a terror attack in Europe were charged in Spain on Sunday with belonging to an unnamed terror organization and possession of explosives, and placed under indefinite detention.

The judge who approved the charges also said a Turkish engineer who worked in Gibraltar for years and was arrested in the same case had paid for Spanish paragliding lessons for the men.

The court named the Russians of Chechen descent as Eldar Magomedov and Mohamed Ankari Adamov and said in a statement there was evidence linking them with "belonging to or forming part of a terrorist organization." The terror group was not specified, but Spanish authorities previously said it was al-Qaida, and the Islamic network has many affiliates.

The two men were driven to the court in dark unmarked government cars under tight security Sunday morning, escorted by police officers wearing masks to hide their identities.