I would say it sounds too much like the plot of Call of Duty 4: Modern Warfare, especially the first mission.. nuclear warhead stowed aboard a merchant ship sailing in the Bering Sea... ship is then sunk by the Russians and the crew is essentially all dead.
Finally found the pix of the Russian naval vessel that sank the Chinese merchant ship. Yeah, it is armed with an AK-230 twin barrel cannon. Here's the link: