European football's governing body UEFA said it was investigating "improper conduct" by Porto supporters and the hearing would take place on March 29.
"Following a complaint lodged by Manchester City, UEFA has today opened disciplinary proceedings against Porto for the improper conduct of supporters," UEFA said in a statement.
Racism is a hot topic in English football at present with Liverpool's Luis Suarez having served an eight-match ban for racially abusing Manchester United's Patrice Evra.
Chelsea captain John Terry is awaiting trial after pleading not guilty to a charge of racially abusing Queens Park Rangers defender Anton Ferdinand during a match last October.
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