Taiwan's government has called China's recent unilateral expansion of civil aviation routes in the Taiwan Strait an irresponsible act that threatens regional security.

China opened several disputed air routes last week, including a northbound M503 route in the Taiwan Strait, without informing Taiwan, contravening what the democratic government in Taipei said is a 2015 deal to first discuss such flight paths.

Taiwan President Tsai Ing-wen, after meeting with ministry heads to assess the situation Sunday, said the move "not only seriously affects aviation safety, but also damages the current situation in the Taiwan strait."