MADRID — Police have arrested three suspected members of Al Qaeda who had amassed explosives and may have been plotting attacks in Spain or elsewhere in Europe, Spain’s interior minister said Thursday. Authorities found evidence suggesting they were experimenting with ultralight planes and remote-controlled planes.
The three — a Russian, a Russian of Chechen descent, and a Turk, according to Spanish police — were detained Wednesday. The Turk was arrested in La Linea bordering the British colony of Gibraltar, while the other two were picked up near Ciudad Real as they traveled toward a town near the border with France.
Enough explosive material was found in the house in La Linea where the Turk lived to blow up a bus, and the material could be especially dangerous if combined with shrapnel, Interior Minister Jorge Fernandez Diaz said.
Investigators found no indications that the three were targeting Gibraltar, he said, declining to offer specifics on possible targets, except that ‘‘there are clear indications they could have been planning an attack in Spain and/or another country.’’
‘‘This is one of the most important operations carried out against Al Qaeda,’’ Fernandez Diaz said. He said the operation involved close collaboration with intelligence services from ‘‘Spain’s allies.’’
The arrests came as the Summer Olympics were being held in Britain under tight security against possible attacks.
Spanish authorities had been watching the suspects for ‘‘some time,’’ the minister said, and decided to arrest them after two of them took a bus toward France.
The two arrested in the bus were traveling from southern Cadiz to Irun, possibly intending to cross into France, the minister said. The pair had been in Spain for about two months. Cadiz is near the large US military base in Rota.
Fernandez Diaz did not disclose the suspects’ names, but said two were suspected Al Qaeda operatives while the Turk was a facilitator. Pictures of the suspects were released by Spanish authorities, but they were identified only by their initials: C.Y. for the Turk and A.A.A. and M.A. for the other two.
The minister described one operative as a key member of the terror network, and said both operatives had practiced flying in light aircraft, without saying where or whether authorities suspect they might have been plotting an attack using aircraft. One was also an expert in explosives and poisonous substances, said Fernandez Diaz.
Spanish police have arrested dozens of Al Qaeda suspects since the Sept. 11, 2001, attacks and more after the 2004 train bombings in Madrid.
Most Islamic-based terror arrests in Spain over the past several years have been of lower-level players and people trying to recruit jihadists, but the detention of the Russians and the Turk was significant because of their apparent high level of training and capability, said Magnus Ranstorp, a terror expert at the Swedish National Defence College.
But getting to Britain during the Olympics probably would have been a challenge for the three, even if they had not been under surveillance.
Passport-free ground travel in much of the 27-nation European Union meant they could have gone to countries on the continent without facing document checks, but getting to Britain is more difficult because passport checks for visitors are mandatory.
The three will appear soon before an investigating magistrate at the National Court in Madrid and remain under detention while a judge decides on possible charges.