Taiwan has claimed that the largest incursion since October by China’s air force took place in its air space on Sunday, Reuters reported. The island country’s defence ministry said that Taiwanese fighters warded off 39 Chinese aircraft.

China sees Taiwan, which is a self-governed territory, as a province that is to be unified with the Chinese mainland. For more than a year now, Taiwan has been complaining against Chinese missions in its air space.

On Sunday, China sent 34 fighter planes, four electronic warfare aircraft and a bomber, the Taiwan defence ministry said, according to Reuters. The aircraft flew in an area to the northeast of the Taiwan-controlled Pratas Islands.

Taiwan sent combat aircraft to warn the Chinese aircraft, while missile systems were deployed to monitor them, the ministry said.

However, China has not made an official statement on the matter yet.

The escalation in the Taiwanese islands has also led to renewed tensions between China and the United States. Washington is Taiwan’s most important international backer and arms supplier, even as the two countries do not have formal diplomatic relations.

Last month, China had warned that it would take “drastic measures” if Taiwan attempted to attain formal independence. The comments came a month after Chinese President Xi Jinping warned his United States counterpart Joe Biden that encouraging the independence of Taiwan would be like “playing with fire”.