The Spanish police arrested a 74-year-old man on suspicion of sending letter bombs to the prime minister’s office, the American and Ukrainian embassies and a weapons manufacturer, among other sites, Spain’s Interior Ministry said on Wednesday.
American officials had said previously that they suspected Russian military intelligence officers had directed associates of a white supremacist militant group to carry out the campaign.
But the Spanish Interior Ministry, in its statement about the arrest, did not mention any possible link between the detained man and either far-right groups or Russia. According to the ministry, the Spanish authorities believe that the arrested man, a Spanish citizen, made and sent all of the six letter bombs himself, though the “participation or influence of other people” was not ruled out.
The ministry did not name the man who was detained, providing only his initials, P.G.P. The statement described him as retired, “very active” on social networks and having “technical and computer knowledge.”
The letter bombs were all sent from the northeastern Spanish city of Burgos, the main city in the Burgos region, the statement said. The man was arrested in a town in that province, and the authorities were conducting a search of the man’s home, where investigators believe he made the explosive devices, the ministry said.
It was not immediately clear from the statement whether the man had been formally charged.
Six letter bombs were sent in late November and early December to sites mostly in Madrid, including Prime Minister Pedro Sánchez’s official residence, which also serves as his office; the two embassies; and the Spanish Defense Ministry.
No one was killed in the attacks, which U.S. officials have described as terrorism. An employee of the Ukrainian Embassy was injured when one of the packages exploded.
One of the letter bombs was also sent to Instalaza, a weapons manufacturer in Zaragoza, in northeastern Spain. Instalaza makes grenade launchers provided to Ukraine by the Spanish government.
Investigators had focused in recent weeks on the Russian Imperial Movement, a group that has members and associates across Europe, according to the U.S. officials, who spoke on condition of anonymity because of the sensitivities around the inquiry.
The officials added that the group, which has been designated a global terrorist organization by the U.S. State Department, is believed to have ties to Russian intelligence agencies.
The apparent aim of the action, according to the U.S. officials, was to signal that Russia and its proxies could carry out terrorist strikes across Europe, including in the capitals of member states of NATO, which is helping defend Ukraine against Russia’s invasion. Spain is a member of the alliance and has given hundreds of millions of dollars in military and humanitarian aid to Ukraine, as well as diplomatic support.