China is holding military drills around Taiwan simulating the seizure and blockade of the island's key areas, as a warning against "separatist forces",
BBC reports.
The army, navy, air force and rocket force have been dispatched for the drills which include live-fire exercises, the Chinese military said.
Codenamed "Justice Mission 2025", the drills are taking place days after the US announced the sale of one of its largest weapons packages to Taiwan worth $11bn (£8.2bn). That move drew sharp protest from Beijing which in turn sanctioned US defence firms.
Taiwan's push to ramp up its defence this year has also angered Beijing, which claims the self-ruled island as its territory.
Taiwan's presidential office has criticised the upcoming Chinese drills, calling them a challenge to international norms.
Its defence ministry said it had detected 89 Chinese military aircraft and 28 warships and coastguard vessels near Taiwan on Monday.
The ministry said separately it had deployed its own missile systems and forces to monitor the situation, adding they are on "high alert" to defend Taiwan and "protect our people".
In a post on Weibo, the Chinese military's Eastern Theater Command - in charge of the Taiwan Strait - described the upcoming military exercise as a "shield of justice".
"All those plotting independence will be annihilated upon encountering the shield!" the post read.
While some initial drills have begun, the military said it would conduct a major exercise from 08:00 to 18:00 local time on Tuesday.
Beijing's foreign ministry called the drills a "severe punishment for separatist forces seeking independence through force" and warned "external forces" against "using Taiwan to contain China".
"Any sinister schemes to obstruct China's reunification are doomed to fail," the ministry's spokesman Lin Jian said at a regular press briefing on Monday.
While China has long called for the "peaceful reunification" with Taiwan, it also has a law stating it will resort to "non-peaceful means" to prevent the island's "secession".