North Korea is reportedly developing a GPS jamming device capable of disrupting signals more than 100 km away. The North has several times disrupted signals in South Korea from Kaesong and Mt. Kumgang. North Korea currently deploys vehicle-mounted jammers capable of disrupting signals within 50-100 km which it imported from Russia in the early 2000s. They are deployed near the Demilitarized Zone. North Korea has about 20 kinds of communications and radar jamming devices that it imported from the former Soviet Union.
The jamming attacks earlier this year by North Korea did have some effect on South Korean weapons and navigation systems using commercial GPS devices. The South Korean military was able to carry on as normal by using alternative equipment like radar and inertial navigation systems. Electronic warfare regiments are deployed in the Pyongyang area and at each of frontline Army corps.