North Korea Tuesday sentenced two South Korean men to hard labor for life on espionage and other charges, state media reported, rejecting repeated calls by Seoul to release them.
The North's Supreme Court handed down life sentences on charges of spying for South Korea's intelligence agency, said Pyongyang's official Korean Central News Agency (KCNA).
The two, identified as Kim Kuk-Gi and Choe Chun-Gil, were also found guilty of trying to topple the communist regime, it said.
The South's Unification Ministry expressed "strong" regret and said it cannot accept the North's unilateral ruling.
The ruling "runs counter to international practices and the spirit of human rights and humanity," the ministry said in a statement, calling for their immediate release and repatriation.
In March, Pyongyang announced the arrest of Kim and Choe saying they had operated as "heinous terrorists" while gathering information about state and military secrets as well as Pyonngyang's leadership.
Choe was arrested last December by border guards, but it was not clear when Kim was detained.
At the time, Kim was accused of spreading "religious propaganda" from an underground church he allegedly ran in the Chinese border city of Dandong.
Choe was accused of recruiting North Koreans to gather soil samples from around the North's main Yongbyon nuclear complex.
The two were among four South Koreans — two of whom were missionaries, according to South Korean church officials — who were detained after illegally entering North Korea.
The North has rejected South Korea's repeated calls to free the four.
Although religious freedom is enshrined in the North Korean constitution, it does not exist in practice and religious activity is severely restricted to officially recognized groups linked to the government.
Pyongyang views foreign missionaries as seditious elements intent on fomenting unrest and those who are caught engaging in any unauthorized activities in the North are subject to immediate arrest.
A number of would-be missionaries — mostly U.S. citizens — have been arrested in North Korea in the past, with some of them allowed to return home after interventions by high-profile American figures.
Last year, North Korea sentenced a South Korean missionary to hard labor for life on charges of espionage and setting up an underground church.
In November Kenneth Bae — a Korean-American missionary sentenced to 15 years' hard labor after being arrested in 2012 — was released following a secret intervention by the US intelligence chief James Clapper.