South Korea's presidential office on Friday dismissed opposition lawmakers' calls for explanations on a relationship between President Moon Jae-in and three activists who were arrested on charges of coordinating with North Korean agents.

The South Korean activists were arrested on Monday on charges of violating the National Security Act by campaigning, under an order from a North Korean operative, against the South Korean military's plans to buy U.S. stealth fighters, according to police.

Under the usual procedure in South Korea, authorities have not identified the activists nor has the identity of their lawyers been disclosed.