NANJING, Dec. 29 (Xinhua) -- Multiple forces of the Eastern Theater Command of the Chinese People's Liberation Army (PLA) started drills code-named "Justice Mission 2025" around Taiwan Island Monday, said Shi Yi, spokesperson for the theater command.

The PLA Eastern Theater Command is dispatching its Army, Navy, Air Force and Rocket Force troops to conduct drills in the Taiwan Strait and areas to the north, southwest, southeast and east of Taiwan Island, Shi said.

The drills will focus on subjects of sea-air combat readiness patrol, joint seizure of comprehensive superiority, blockade on key ports and areas, as well as all-dimensional deterrence outside the island chain, he added.

"With vessels and aircraft approaching Taiwan Island in close proximity from different directions, troops of multiple services engage in joint assaults to test their joint operations capabilities," he said.

It is a stern warning against "Taiwan Independence" separatist forces and external interference, and a legitimate and necessary action to safeguard China's sovereignty and national unity, he said.