My wife found this on a Russian website and they're claiming it's American cargo marked as Humanitarian Aid.

 I did a quick search and found a couple of English written articles. One was saying that the Greek authorities have not disclosed the country of ownership. I was surprised to find that this artilce is five days old. 5000 shotguns and 500,000 rounds of ammunition.

http://www.independent.co.uk/news/world/middle-east/greek-coastguards-se... (link is external)

http://www.reuters.com/article/2015/09/02/us-libya-security-greece-arms-... (link is external)