Rigters had been linked with a host of British clubs, including Newcastle, Celtic, Rangers and Norwich.
Blackburn chairman John Williams said: "We have been following him for some time after Mark Hughes identified him as a player he would be interested in."
Rigters' arrival however could be an indication that Blackburn expect to lose Benni McCarthy.
The free-scoring South African striker has made no secret of the fact he would like to be at a club playing in the Champions League.
Rigters is Blackburn's second capture of the summer - it came hours after the signing of goalkeeper Gunnar Nielsen.
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