The U.K.'s Ministry of Defence said Tuesday that four members of its military have been arrested under the Terrorism Act on suspicion of belonging to National Action, a banned neo-Nazi group, and planning terrorist acts, per Reuters.

The four arrests were made by counter-terrorism officers in the English cities of Birmingham, Ipswich, and Northampton, and in Powys, Wales. "The arrests were pre-planned and intelligence-led; there was no threat to the public's safety," West Midlands Police said.

Why it matters: National Action became the first far-right group to be outlawed in Britain last year after the group praised the murder of Jo Cox, a member of parliament who was killed by a man motivated by Nazism and white supremacist ideology. Meanwhile, the U.K.'s threat level is currently ranked as "severe," the second-highest level, meaning an attack is highly probable.