Not all North Korean fishing boats are brought to the South for investigation.
With that, the defense officials acknowledged that this type of projectiles could reach Japan as, based on findings of the US and South Korean military, the ones launched on Thursday flew about 600 km (373 miles), the report added.
It additionally stated the ship's captain was knowledgeable of the crew's planned launch about three hours earlier than their departure from North Korea's Wonsan port.
The JCS official also said that while one crew member was clad in a military uniform, it remains unconfirmed whether he is anactive-duty soldier.
Seoul's Unification Ministry said in a statement it chose to let the North Koreans return home in line with their wishes.
"Repatriation is taking place according to the free will" of the boat crew, the ministry added.
South Korea notified Pyongyang that the crew members had willingly left a South Korean port for the North, the ministry in charge of inter-Korean affairs said in a statement. The boat then crossed into the South at 11:21 a.m.
The Russian fishing boat Xiang Hai Lin 8, released on Saturday after being detained by North Korean border patrol officers, has arrived at a port in Sokcho, South Korea, Yonhap reported on Sunday referring to the Ministry of Unification.
The ministry said it considered the release positive from a humanitarian standpoint. The 10-meter-wooden boat was also towed.
Many other foreigners who admitted to crimes against North Korea at news conferences have said after their releases that their confessions were given involuntarily and under duress, making Kim's comments doubling down on his spying that much more significant.