The number is based estimated from two of the volunteers interviewed by news agency TT. And they say that although the reasons for joining the Ukrainian government's "anti-terror operation" vary, the unifying idea has to do with Ukraine's right to self-governance - both with regards to Russia and the European Union.
In an email to TT, Fredrik, who's a 37-year-old father, explains that he was involved in nationalistic organisations in his youth, but says that his main reasons for going was to form his own opinion of what was happening. His feeling was that both Russia and the West was trying to control Ukraine. "For me it wasn't all that difficult to find my way to where I am today and actively work for Ukraine getting the chance to set its own path," he writes.
Another volunteer is Mikael Skillt, previously an active member of the neo-nazi Party of the Swedes (Svenskarnas parti). He is one of a reported four Swedes to have joined the Azov Battalion, based in the port city of Mariupol near the Azov Sea.
The battalion consists of volunteers from Ukraine as well as other countries, many of whom have strongly held right-wing extremist or neo-nazi beliefs. Skillt tells TT that for him, the fight is about an ethnically homogenous Ukraine. But he says not everybody in the battalion shares his beliefs.