They were among 11 men - aged between 22 and 35 - arrested on Wednesday, with the other six remaining in custody, West Yorkshire Police said.
Two men from Swansea, aged 28 and 23, were released along with a 23-year-old from Sowerby Bridge, West Yorkshire, a 26-year-old from Leeds and a 30-year-old from Wiltshire.
The arrests were made by officers from Counter Terrorism Policing North East and North West, supported by Wales Extremism and Counter Terrorism Unit and Wiltshire Police.
National Action became the first extreme right-wing group to be banned under terrorism laws in December 2016.
The proscription meant that being a member of or inviting support for the organisation is a criminal offence carrying a sentence of up to 10 years’ imprisonment.