MADRID >> Police have arrested three suspected members of al-Qaida who had amassed explosives and may have been plotting attacks in Spain or elsewhere in Europe, Spain’s interior minister said today. Two of them had practiced flying light aircraft.

The three — a Russian, a Russian of Chechen descent, and a Turk, according to Spanish police — were detained Wednesday. The Turk was arrested in the southern city of La Linea bordering the British colony of Gibraltar, while the other two were picked up near the central city of Ciudad Real as they traveled toward a northern Spanish 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-Qaida,” Fernandez Diaz told reporters. He said the operation involved close collaboration with intelligence services from “Spain’s allies,” without identifying any of the countries. 

The arrests came as the Summer Olympics were being held in Britain under tight security against possible terrorist attacks, including military aircraft and ground-to-air missiles. 

Spanish authorities had been watching the suspects for “some time,” the minister said and decided to arrest them after the Russian and the Russian of Chechen descent took a bus toward France. 

The two arrested in the bus were traveling from southern Cadiz to the northern town of 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 U.S. military base in Rota alongside the Mediterranean. 

“Police moved to arrest them when it became known that they planned to leave Spain,” he said.

Fernandez Diaz did not disclose the suspects’ names, but said two were suspected al-Qaida 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 mug shots showed three men who appeared to be in their 30s, two with crew cuts and one with hair down to his shoulders. 

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.