U.S. authorities have arrested a former marine in connection with a mysterious February raid on North Korea's embassy in Spain during which masked assailants roughed-up staff and stole computers, the Washington Post reported Saturday.

Citing two sources familiar with the case, the Post said federal authorities arrested Christopher Ahn, a former US Marine and member of a group dedicated to the overthrow of North Korean leader Kim Jong Un.

A dissident organisation known as the Cheollima Civil Defense (CCD) said it had orchestrated the February 22 embassy raid to highlight illicit activities rampant in North Korea's foreign missions.

It came just days before a high-stakes nuclear summit in Vietnam between Kim and US President Donald Trump that ultimately failed to reach an accord. The Post said federal agents had also searched the apartment of Adrian Hong Chang, a Mexican national who Spanish authorities said last month had led the embassy raid.

An FBI spokesman referred questions on the case to the Justice Department, who declined to comment.