North Korea's rare swipe at China this week underscored how Beijing and Pyongyang do not entirely see eye-to-eye on the latter's illicit nuclear weapons arsenal, despite warming ties in other areas, analysts and officials in South Korea said.

The North condemned China, Japan and South Korea on Monday for discussing denuclearization of the peninsula, calling their joint declaration after a summit in Seoul a "grave political provocation" that violates its sovereignty.

Even though Beijing helped tone down the statement by advocating mention of the peninsula rather than the North specifically, that was enough to raise its neighbor's hackles, one analyst said.