Children - some believed to be as young as 10 - attacked PSNI vehicles after the 32 County Sovereignty Movement event took place at City Cemetery.
A statement from police said: "While the event passed off without incident it was extremely concerning to see children, some of whom looked to be under the age of ten, throwing stones at police vehicles.
"It is a sad indictment on those who organised and were in attendance that this was allowed to happen."
Around 300 people attended the commemoration on Monday afternoon.
Officers maintained a low-key presence and issued two verbal warnings to those taking part in the illegal procession.
In previous years it has been addressed by masked dissident representatives, but there was no paramilitary statement this year.
There have been no reports of any arrests.
Police said they will be making further inquiries.