Daniel Andreas San Diego, 46, wanted by the FBI for a pair of San Francisco-area bombings in 2003 was arrested in the United Kingdom. FBI

An alleged animal rights activist wanted for two bombings in the San Francisco area was arrested this week in Britain after more than 20 years on the run.

Daniel Andreas San Diego, 46, one of the FBI's most wanted fugitives, was nabbed Monday in northern Wales.

He was charged in the U.S. in August 2003 for the bombings on the campus of Chiron Life Science Center, a biotechnology company, in Emeryville, Calif., and another a month later at a nutritional products company in Pleasanton, Calif.

The bombings did not hurt anyone, but the explosive device at the biotechnology company was designed to hurt first responders, the AP said.

A group that called itself the Revolutionary Cells-Animal Liberation Brigade claimed responsibility for the bombings, saying the companies were linked to Huntingdon Life Sciences, which had been targeted by animal rights activists for testing chemicals on animals, the Associated Press reported.

"Daniel San Diego's arrest after more than 20 years as a fugitive for two bombings in the San Francisco area shows that no matter how long it takes, the FBI will find you and hold you accountable," 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."

San Diego became the first person suspected of domestic terrorism to be added to the FBI's Most Wanted Terrorist List, the AP said, and a $250,000 reward was offered for information leading to his arrest.

He was last seen in 2003 as FBI agents were closing in on him in San Francisco, the BBC reported.

"He parked his car, got out of his vehicle and started walking down the street and if I'm not mistaken, he went into a Bart [train] station and that was the last time we've seen him," David Johnson, an FBI agent, recalled in 2013, the report said.

He is in custody while awaiting extradition to the United States.