North Korea will repatriate a 21-year-old South Korean student who has been detained there since April, the Unification Ministry said Monday, in what could be a conciliatory gesture by the North to South Korea.

The communist  nation will repatriate Joo Won-moon, a New York University student alleged to have attempted to illegally cross the border from China, through the truce village of Panmunjom at 5:30 p.m. today, according to a ministry official. The North informed the South of the plan via fax.

"It's a relief that North Korea has decided to repatriate our national, Joo," the official noted, adding that the North should also send back home three other South Koreans now held in the country.

The move comes as North Korea has ratcheted up its missile and nuclear threats, raising tension on the Korean Peninsula following the hard-won conciliatory mood over long-strained inter-Korean ties.

South and North Korea reached a landmark deal on Aug. 25 to defuse military tension and resume the reunions of families separated by the 1950-53 Korean War.

But the North has vowed to launch a long-range rocket or hinted at conducting a fourth nuclear test as it is preparing for the 70th anniversary of the founding of the ruling Workers' Party of Korea, which falls on this Saturday.

In an interview with U.S. news cable network CNN in May, Joo admitted that he had intentionally entered the North on the belief that his arrest could have a good effect on inter-Korean relations.

With the repatriation of Joo, the North is holding three South Koreans -- missionary Kim Jung-wook, Kim Kuk-gi and Choe Chun-gil.

The North has held the 52-year-old Kim Jung-wook in captivity since October 2013, calling him a spy for South Korea's National Intelligence Service, who sneaked into the country with the purpose of inciting dissent. He was sentenced to hard labor for life in May 2014.

In June, the North handed down the same sentence to the other two South Koreans for spying for the South's intelligence agency. (Yonhap)