MADRID—A Spanish judge is questioning two Russian men suspected of plotting a terror attack in Spain or elsewhere Europe to decide whether to charge them.

The two, who are both of Chechen origin, were escorted by masked police Sunday to the National Court in Madrid.

A Turkish national with whom they have been linked was charged Friday with the possession of explosives and a device likely to be used in a terror attack.

The interior minister has described the Russians as suspected al-Qaida members and said the Turk is suspected of being a facilitator for the terror group. The Turk was arrested Thursday in the southern city of La Linea while the Russians were picked up Wednesday as they traveled by bus towards the French border.

A court official says Judge Pablo Ruz of the National Court is hearing evidence Sunday that will determine whether he charges the Russians. The official spoke on condition of anonymity due to court rules.

The Turk had operated for years in Gibraltar and the explosive material was seized in his house in the southwestern Spanish city of La Linea, just across the border from the British colony and naval base.