Vietnam says China's plan to move its first deep-water drilling rig into the disputed South China Sea, one of Asia's most volatile hotspots, is illegal and has called for the rig to be removed from what it says is Vietnam's territorial waters. The $1 billion offshore oil rig called Haiyang Shiyou 981 owned by the China's state-run CNOOC oil company has been drilling south of Hong Kong. Maritime Safety Administration of China (MSAC) on Saturday published an announcement on its website saying it prohibits all marine vessels entering into a one mile radius of the Haiyang Shiyou 981's South China Sea drilling work. Vietnam's Foreign Ministry spokesman on Sunday objected to the move…