Ex - S. Korean general suspects a North Korean tunnel is under a Seoul apartment complex . But the Korean Defense Ministry believes tunnels ca n't exist beyond 6 km from the city . A source says tunnel operations began in the 1980s .
Ex-S. Korean general suspects a North Korean tunnel is under a Seoul apartment block . But S. Korean Defense Ministry believes tunnels ca n't extend beyond 6 miles from the DMZ . A defector says tunnel operations peaked in the 1980s .