The navies of Japan, South Korea and the United States held a rare joint missile defense exercise Sunday in the Sea of Japan, as North Korea’s continued weapons tests push trilateral security ties closer than ever.

South Korea’s Navy said in a statement that Sunday's exercise, which was conducted in international waters and involved Aegis destroyers from the three countries, focused on practicing detecting and tracking a computer-simulated ballistic missile target and sharing related information.

The Maritime Self-Defense Force said in a separate statement that the drills — the fourth of their kind since South Korean President Yoon Suk-yeol took office — were “intended to vigorously promote trilateral cooperation to address regional security challenges amid the increasingly severe security environment surrounding Japan.”