In my opinion you should use "there are".
This is a question of the mood of the verb. "There are" is the indicative mood and "there be" is the subjunctive mood. The subjunctive has become rare in BrE, but is still sometimes heard in AmE. In this case, however, I think that nowadays most fluent speakers would say "there are riots."
Having said that, I must add that it is unnatural to say "there are riots between." Although when riots occur it is often obvious that there are opposing parties, one often does not know exactly who the rioting parties are or what their agenda is.
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