The ministry said that the exercise in the Bohai Gulf was aimed at “boosting the forces expulsion mission capability” and not at any specific nations or targets. The drills had been pre-planned as part of routine training, according to the statement posted late Wednesday on the ministry’s official Sina Weibo microblog account.

While it is usual for the Chinese military to hold drills in the Bohai Sea off its northeastern coast, the timing of Tuesday’s exercise has drawn special attention. China has repeatedly said it will not tolerate an armed conflict on its doorstep and says there can be no military solution to the current tensions on the Korean Peninsula.

In May, China test-fired a new type of missile into the Bohai Gulf amid anger over South Korea’s deployment of a sophisticated U.S. anti-missile system to which China has fervently objected. The feud, which shows no sign of waning, has severely impacted diplomatic and economic ties between the two countries.

The Bohai Gulf lies just west of the Yellow Sea, which separates China from the Korean Peninsula.

Outside experts have been unable to verify North Korea’s claim that it tested a hydrogen bomb Sunday, but say it’s plausible.

China’s defense ministry last week said that it had not made any changes to its military posture on the North Korean border.