The unification ministry on Tuesday called on North Korea to "immediately and unconditionally" release Choi Chun-gil, a South Korean missionary detained in North Korea and five other nationals on the occasion of marking 10 years since his arrest.

Choi is among six South Koreans who have currently been in detention for years in North Korea, including two other missionaries -- Kim Jung-wook and Kim Kook-kie. Choi was arrested in December 2014 and sentenced to hard labor for life on the charge of spying for South Korea's intelligence service.

The unification ministry denounced North Korea's practice of "unjustly and arbitrarily" detaining the missionaries as a "blatant" attempt to oppress freedom of religion or belief and silence international calls for improving its human rights situation.

"The ROK Government strongly urges the North, which is a party to major international human rights instruments, to immediately and unconditionally release our nationals who are illegally detained," the ministry said in a statement, using the acronym of South Korea's official name, the Republic of Korea.

The ministry condemned North Korea for unreasonable and excessive sentencing of the six individuals without a fair and public trial; its failure to provide basic procedural justice upon arrest and during detention; and the continued arbitrary detention.

The government said it will continue its efforts to confirm the fate of the detained South Koreans in close cooperation with the international community. (Yonhap)