Police arrested three alleged al-Qaeda members who were plotting a terrorist attack in Spain or Europe, government authorities made known on Thursday. \'\'There was evident proof\'\' that they were planning a fatal terrorist attack on unknown targets \'\'in Spain or other European countries,\'\' Interior Minister Jorge Fernandez Diaz told reporters. The men, two Chechens and one Turk, were arrested late last night to stop them from leaving the country, authorities said. The arrests follow a two-month investigation by Spanish police and allied countries\' intelligence, which the minister described as \'\'one of the most extensive investigations into al-Qaeda on an international level.\'\' The Chechens, whom authorities said are \'\'extremely dangerous,\'\' were intercepted in Almaduriel, near Ciudad Real in the Castille La Mancha region. They were on board a bus traveling from Cadiz to Irun, in the Basque Country. Their intention was to cross the border into France, authorities said. One of the two \'\'is an extremely important figure in al-Qaeda\'s international structure,\'\' the minister said. The Turk, whom authorities described as a \'\'facilitator\'\' within the terrorist cell, was arrested in the Andalusian resort town of La Linea de Concepcion, where an arsenal was found in his apartment. \'\'There was enough explosive material to blow up a bus, and it would have been especially lethal because they added metal fragments to it,\'\' Diaz said. The operation follows on the arrest in June of two Spanish citizens of Arab origin in Melilla, the Spanish enclave on Moroccan soil. They allegedly belong to a particularly violent jihadist cell. They share \'\'the same radical orthodoxy\'\' as the suicide bombers who blew themselves up in Leganes, south of Madrid, just days after the Atocha train station bombing of March 11, 2004, which left 1.500 wounded and 190 people dead, the minister explained.