Daniel Andreas San Diego, 46, was one of the FBI’s “most wanted terrorists” for two bombings in the San Francisco area in 2003.
Two bombs exploded about one hour apart on the campus of a biotechnology corporation in Emeryville in August that year, according to the agency.
Then, in September of the same year, one bomb strapped with nails exploded at a nutritional products corporation in Pleasanton.
According to the FBI, San Diego has ties to “animal rights extremist groups” and there was a reward of $250,000 (£199,000) for information leading directly to his arrest.
FBI Director Christopher Wray said: “There’s a right way and a wrong way to express your views in our country, and turning to violence and destruction of property is not the right way.”
The UK’s National Crime Agency (NCA) made the arrest on Monday, the organisation confirmed, in the Conwy area of Wales.
It is understood he was arrested at a property in a rural area next to woodland.
He appeared at Westminster Magistrates’ Court on Tuesday as the process to extradite him to the US to face charges begins.
“Daniel San Diego’s arrest after more than 20 years… shows that no matter how long it takes, the FBI will find you and hold you accountable,” Mr Wray added.
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The FBI claims he is known to follow a vegan diet and has worked as a computer network specialist.
He is also “known to possess a handgun”, the agency said on its website, and has a tattoo on his chest with the words “it only takes a spark”.
That tattoo, along with others, may have been “altered or covered”.
