It was during Thursday that the men were requested to be detained on probable cause, the higher degree of suspicion. All are aged 50-55, of which two are natives of Western Sweden and one in the Stockholm area.
Two of the men are suspected of gross crimes against international law committed in Syria between July and September 2012. For the third man, the suspicions extend to September 2013.
All were arrested early on Wednesday morning and arrested later in the day.
The effort has taken place within the framework of a collaboration between Swedish and German prosecutors and police with the support of Europol and Eurojust.