According to a Spanish Interior Ministry statement, Villota, who is originally from Bilbao, has lived with false documents in the UK and has been "waiting for instructions" from Eta.
The Ministry says Villota was recruited in 1990 to join the legal Matalaz Command, under the Command Vizcaya.
More top news
These are the three men police want to speak to in connection with the assault of a teenager in Manchester’s Gay Village.
Detectives have been given more time to question a terror-plot suspect held after raids in Lancashire on Thursday.
Rail passengers using the West Coast Main Line will experience major disruption from today as engineering work begins in Warrington.