China launched live-fire drills around Taiwan on Monday that it said would simulate a blockade of the self-ruled island's key ports, prompting Taipei to condemn Beijing's "military intimidation".
Beijing claims Taiwan as part of its sovereign territory and has refused to rule out using military action to seize the island democracy.
The latest show of force follows a bumper round of arms sales to Taipei by the United States, Taiwan's main security backer.
Beijing warned on Monday that "external forces" arming Taipei would "push the Taiwan Strait into a perilous situation of imminent war", but did not mention any countries by name.
Any attempts to stop China's unification with Taiwan were "doomed to fail", foreign ministry spokesman Lin Jian said.
China said earlier it was conducting "live-fire training on maritime targets to the north and southwest of Taiwan" in large-scale exercises involving destroyers, frigates, fighters, bombers and drones.
A military spokesman said Beijing would send army, navy, air force and rocket force troops for "major military drills" code-named "Justice Mission 2025".
The activities will focus on "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", said Senior Colonel Shi Yi of the People's Liberation Army's Eastern Theater Command.
Chinese authorities also published a map of five large zones around Taiwan where further live-fire activities would take place from 8:00 am to 6:00 pm (0000 to 1000 GMT) on Tuesday.
"For the sake of safety, any irrelevant vessel or aircraft is advised not to enter the afore-mentioned waters and airspace," the statement said.
- 'Rapid response' -
Taiwan condemned China's "disregard for international norms and the use of military intimidation to threaten neighboring countries", Presidential Office spokeswoman Karen Kuo said.
Taipei said Monday it had detected four Chinese coastguard ships sailing off its northern and eastern coasts.
Its coastguard said it "immediately deployed large vessels to pre-position responses in relevant areas" and "sent additional support units".
Taiwan's military said it had established a response center, deployed "appropriate forces" and "carried out a rapid response exercise".
The drills by China's ruling Communist Party "further confirm its nature as an aggressor, making it the greatest destroyer of peace", Taipei's defense ministry said.
- 'Stern warning' -
Shi, the Chinese military spokesman, said the drills were "a stern warning against 'Taiwan Independence' separatist forces, and... a legitimate and necessary action to safeguard China's sovereignty and national unity".
Beijing's military released a poster about the drills showing "arrows of justice" -- one engulfed in flames -- raining down on what appeared to be green worms on a geographical outline of Taiwan.
Chinese state broadcaster CCTV reported that a core theme of the exercises was a "blockade" of key Taiwanese ports including Keelung in the north and Kaohsiung in the south.
China's military last held large-scale drills involving live firing around Taiwan in April -- surprise maneuvers condemned by Taipei.
China said this month it would take "resolute and forceful measures" to safeguard its territory after Taiwan said the United States had approved a major $11 billion arms sale.
Beijing announced fresh sanctions on 20 American defense companies last week, though they appeared to have little or no business in China.
Last month, Japan's Prime Minister Sanae Takaichi triggered a backlash from Beijing when she said the use of force against Taiwan could warrant a military response from Tokyo.
