Taiwan’s Defense Ministry said Tuesday it had detected 59 Chinese military aircraft and nine navy vessels operating around the island over the past 24 hours as part of “joint combat patrols,” days after the democratic island’s president called Beijing “a foreign hostile force.”

The aircraft tally was the highest reported for a single day near Taiwan since October, when China’s military held massive drills around the island. The Defense Ministry in Taipei said it was closely monitoring the exercises.

China’s Foreign Ministry said the move was intended as a warning to Taipei and “external forces” backing its formal independence — a veiled reference to the United States.