Swiss authorities say they arrested three Iraqi citizens in March who are suspected of providing support to the Islamic State (IS) extremist group and planning a terrorist attack in Europe.
The public prosecutor said on October 31 that the trio is also suspected of using explosives and toxic gases with criminal intent, of pornography offences, and encouraging illegal entry to the Alpine country.
The three, who have not yet been charged, are still in detention while investigations continue.
Prosecutors said Swiss investigators, with assistance from European and U.S. officials, are attempting to identify possible accomplices and to uncover networks both in Switzerland and elsewhere.
IS militants control large swathes of territory in Iraq and Syria.