The South Korean military says a pair of Russian aircraft violated South Korea’s air defense identification zone(KADIZ) last week.

According to a South Korean military official on Wednesday, several South Korean fighter jets were scrambled after two Tupolev Tu-142 Russian warplanes entered the zone near the southern island of Jeju last Friday. 

The official said the South Korean military did not take additional measures after it had established contact with the pilots of the Russian planes.

Various details remain unknown, including the number of times the aircraft infiltrated the zone that day. The Russian aircraft were presumed to have been mobilized recently for a joint military exercise between Russia and China near the Chinese port city of Qingdao. 

The incident comes ten months after two other Russian military planes violated the KADIZ four times in a 24-hour period, prompting the South Korean government to summon a Russian military attache to protest.