Those arrested are accused of involvement in crimes of murder, possession of weapons and explosives and acts against the interests of Spain abroad.
The ministry spokesman said that all the detainees had been fighting "on the same side", however he could not confirm nor specify whether they fought alongside Kiev forces or independence supporters. Neither the time they spent in Ukraine, nor the date when they returned to Spain, is known yet.
The eight were detained at 05:30 GMT on Friday during a raid that took place in several different regions across Spain — Asturias, Catalonia, Extremadura, Madrid, Murcia and Navarre.
An armed conflict broke out in Ukraine`s southeast last April, after Kiev launched a military operation against the region`s pro-independence movement.
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