China sent 57 planes and four warships close to Taiwan in the 24 hours before 6am on Monday, in what appeared to be a part of joint navy and air force combat drills announced by the People's Liberation Army’s Eastern Theatre Command late on Sunday.
In a chart of the PLA aircraft flight paths released by the Taiwanese defence ministry on Monday, 28 of the planes appeared to be blocking off three sides of the self-ruled island.
In a statement accompanying the chart, the ministry said 23 of the planes had crossed the median line between the island and mainland China. These included 12 J-16 fighter jets, two Sukhoi Su-30 fighters, two J-10s, six J-11s and one KJ-500 early warning plane.
Two nuclear-capable H-6 bombers and three BZK-005 reconnaissance drones were also detected entering Taiwan's southeast air defence identification zone, the ministry said.
Taipei's Presidential Office condemned the PLA drills in a statement issued on Monday, saying they intensified cross-strait and regional instability.
"Through various ungrounded claims and reasons, the communist forces have persistently carried out military operations around Taiwan in recent days. For this, the Presidential Office voices its grave condemnation," spokesman Xavier Chang said.
Chang said the two sides of the Taiwan Strait shared a responsibility to uphold peace and stability in the region. Taiwan would never provoke or escalate conflict, and the military had the resolution to defend the island and safeguard its public, he said.
Announcing the drills on Sunday night, PLA Eastern Theatre Command spokesman Senior Colonel Shi Yi said its forces had organised "joint combat readiness patrols and actual combat drills in the sea and airspace around Taiwan, focused on land strikes and sea assaults".
"The purpose of the drills is to test joint combat capabilities and also to resolutely counter the provocative actions of external forces and Taiwan independence separatist forces," Shi said in a written statement.
This is the second time in less than a month that the PLA has organised high-intensity exercises near the island. On Dec 25, a record 71 warplanes and four ships were spotted operating around the island, according to the Taiwanese defence ministry.
In the latest operation, the PLA planes which crossed the median line - a de facto border through the Taiwan Strait separating the island from the mainland - briefly approached the north and west of the island, the ministry said.
The KJ-500 and BZK drones which headed to Taiwan's southeast adopted a flight pattern which appeared to form a blockade, according to the chart released by the ministry.
"The [Taiwanese] armed forces have monitored the situation and tasked combat and air patrol aircraft, navy vessels and land-based missile systems to respond to these activities," the ministry said.
Observers in Taiwan said the latest exercises were intended as high-intensity training for PLA forces to strengthen their combat capabilities.
"By mobilising different types of planes and ships from different air and naval ports, the PLA was practising joint combat operations, including at night," said Chang Yen-ting, a former Taiwanese air force vice commander.
Chang said the PLA was hoping to create "a new normal" with its increasing number of crossings of the median line and frequent fly-bys of areas close to the island's contiguous zone, as well as entering the 24-nautical-mile territorial space around Taiwan.
"By edging closer every time, such fly-bys or crossovers would eventually wear down the guard of Taiwanese people against any potential attacks by the PLA in the future," he said.
Observers said the latest drills were also intended to serve as a warning to the US for allying with the island and other forces - including from Japan - in countering the PLA.
"The drills followed recent US military operations near Taiwan and they could be a message for the Pentagon that [Beijing] will not tolerate such actions," said Lin Ying-yu, a professor of international relations and strategic studies at Tamkang University in New Taipei.
Last week, the US sent the Arleigh Burke-class guided-missile destroyer USS Chung-Hoon (DDG 93) for a "routine" transit of the Taiwan Strait "through waters where high-seas freedoms of navigation and overflight apply in accordance with international law".
The latest mass fly-bys follow US President Joe Biden's signing late last week of the National Defence Authorisation Act, a defence spending bill which includes the Taiwan Enhanced Resilience Act to increase military aid and security cooperation for the island.
Most countries, including the US, do not recognise Taiwan as an independent state. Washington, however, opposes any attempt to take the island by force, which has not been ruled out by Beijing in its pledge to reinstate mainland control.
Chang, the former Taiwanese air force officer, said the drills could also be a sign of protest from Beijing over this week's meetings in Washington between heads of defence and foreign affairs from the US and Japan.
US Defence Secretary Lloyd Austin and Secretary of State Antony Blinken will host talks on security and cooperation with their Japanese counterparts - Yasukazu Hamada and Yoshimasa Hayashi, respectively - on Thursday.
The "2+2" meeting will discuss security challenges and cooperation on ways to achieve a "free and open Indo-Pacific," the Japanese defence ministry said.
The meetings will be followed by talks between Japanese Prime Minister Fumio Kishida and Biden at the White House on Friday.
This article originally appeared on the South China Morning Post (SCMP) website.
