The Spanish Interior Ministry said on Wednesday that the police had arrested a 74-year-old man on suspicion of carrying out a recent letter bomb campaign, which U.S. officials have said was intended to signal how Russia and its proxies could carry out terrorist strikes in NATO member states.
The arrest of the man, a Spanish citizen, comes days after American and European officials said they believed that Russian military intelligence officers had directed associates of a white supremacist militant group based in Russia to carry out the attacks.
Investigators have 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.
According to a statement from the Interior Ministry, the Spanish authorities believe that the man who was arrested made and sent all of the six letter bombs himself, though the “participation or influence of other people” was not ruled out. The statement made no mention of any link between the man, who police investigators said had “technical and computer knowledge,” and either far-right groups or the Russian government.
The letter bombs were all sent from the northeastern Spanish city of Burgos, the main city in the region of Burgos where the man was arrested, the statement said.
The 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 American and Ukrainian embassies; and the Spanish Defense Ministry.
No one was killed in the attacks, which U.S. officials consider terrorism. An employee of the Ukrainian Embassy was injured when one of the packages exploded.
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.
One of the letter bombs was also sent to Instalaza, a weapons manufacturer in Zaragoza, northeastern Spain. Instalaza makes grenade launchers provided to Ukraine by the Spanish government.
U.S. officials said that the Russian officers who directed the campaign appeared to be intent on keeping European governments off guard and may be testing out proxy groups to carry out such attacks.