Upvote:3
AFAIK no country supplied troops in anything approaching an official capacity.
Of course that doesn't mean they weren't there, but if they were there it would not be something the countries in question would want to be known so it's highly unlikely you're going to find official sources to corroborate any claims.
More likely is that some international mercenary companies signed up with one combatant or the other (or even both) to provide specialty services and staff. That too would not be documented anywhere in public view. Those groups are rather secretive by nature (of course) and so are the parties hiring them.
I seriously doubt that either channel would lead to a large number of foreigners from any one country serving on either side.