That is a good question. There is anecdotal evidence linking them to Russia. But a lot more study needs to be done in part because a lot of the weapons listed that we've seen are early-generation, Soviet-designed systems that were widely exported in the region and were stockpiled by Ukraine. There are exceptions and I can talk about those exceptions, but a more systematic analysis is needed.
On October 18th, 2017. See this statement in context.