Radio intercepts sent to Newsweek included at least 17 airborne warnings aimed at People’s Liberation Army (PLA) warplanes. The warnings were broadcast by Republic of China Air Force (ROCAF) radio operators between 5:48 a.m. and 10:43 a.m. local time, but the precise number of intruding aircraft was initially unclear.

Reached by Newsweek, the office of Taiwan’s Ministry of National Defense spokesperson declined to comment on these developments. The department later announced that it had detected 28 Chinese military planes—a single-day record.

A radio log of activity in Taiwan’s self-declared air defense identification zone (ADIZ) showed PLA aircraft were detected at altitudes between 5,000 and 7,800 meters (about 16,400 and 25,600 feet).

According to the transcript of correspondence on the aeronautical emergency frequency 121.5 MHz, at least one Chinese pilot responded to a ROCAF broadcast at 9:20 a.m., identifying himself as a member of the PLA Naval Air Force “conducting a routine mission.”

Newsweek could not independently verify the accuracy of the exchange.

The large incursion into the southwest corner of Taiwan’s ADIZ comes after 10 days of relative quiet, with just one PLA asset detected in the area since June 4—a Y-8 anti-submarine warfare aircraft spotted on Monday, a public holiday in both China and Taiwan.

The Chinese military’s return to “gray-zone” activity around Taiwan follows President Joe Biden’s attendance of key summits with G7 and NATO allies, both of which resulted in firm rebukes of Beijing’s actions across various sectors.

Monday’s NATO joint statement highlighted China’s ambitions and assertive behavior, which “present systemic challenges to the rules-based international order and to areas relevant to Alliance security.”

The leaders raised concerns about “coercive policies,” its expanding nuclear arsenal as well as the lack of transparency in its ongoing modernization of the PLA.

“We see coercive behavior, for instance in the South China Sea, and we also know that China does not share our values,” NATO Secretary General Jens Stoltenberg told reporters in Brussels.

“We need to respond together as an alliance,” he added.

Following three days of deliberations in England, Biden led G7 leaders in a communique that included several direct and indirect mentions of China, pushing Beijing for cooperation in COVID-19 origin tracing, fair trade practices and human rights.

The statement on Sunday also expressed serious concerns about developments in the East and South China Seas. Notably, it called for peace and stability across the Taiwan Strait.

The Chinese Embassy in London responded on Monday by decrying “wanton smearing of China and blatant interference in its internal affairs,” according to a statement posted on its website.

At a press briefing in Beijing on Tuesday, Chinese Foreign Ministry spokesperson Zhao Lijian described the G7’s statement as an attempt to form a “clique” to suppress China’s development.

Su Tzu-yun, an associate fellow at the Institute for National Defense and Security Research in Taipei, said the renewed warplane activity near Taiwan follows a period of “strategic adjustment” by Beijing.

“China feels that its Wolf Warrior diplomacy is facing many challenges, so Xi Jinping wants to promote a more credible, lovable and respectable image,” Su told Newsweek.

“Militarily, China was also searching for a new tempo, so there was a period of quiet. But the nature of China’s military use has always been 70 percent politics and 30 percent military, so its warplane activity in the area also follows this logic,” he added.

The analyst believes China is under international pressure following multiple U.S.-led joint statements and the recent communiques by the G7 and NATO. The U.S. Navy’s Ronald Reagan Carrier Strike Group is in the South China Sea, while the U.K.’s Royal Navy flagship HMS Queen Elizabeth is also headed for the Indo-Pacific region.

“These are big diplomatic and military signals for China,” said Su, who believes “domestic demand necessitates action by the PLA for domestic propaganda,” especially ahead of the Chinese Communist Party’s centennial on July 1.

Update 6/15/21, 6:55 a.m. ET: This article has been updated with the latest Defense Ministry figures.