China started a military exercise in the Bohai Sea on Sunday afternoon, according to the Liaoning Provincial Maritime Safety Administration.
The administration published a navigational notice on its website late Saturday night saying there will be military drills in the northern parts of the sea from 12 to 8 pm on Sunday.
It released the geographical coordinates of the drill zones, asking other ships not to enter.
In an announcement published by the administration on Friday, military operations will take place in the Bohai Sea from 4 pm on Sunday to 4 pm on Aug 20.
Whether the two announcements are correlated remains unknown, as the People's Liberation Army or other authorities have yet to publish more details.