Not SA-2s but rather AAA guns, possibly KS-19s (100 mm) or S-60s (57 mm). They look similar and there's not enough resolution in this image to tell for sure.
Their size and general shape lead me to believe they are KS-19s, radar-controlled 100mm AAA guns. The North Koreans have thousands of these guns, which make up a big portion of their air defense capability. Finding and killing every AAA gun in North Korea would be pretty much impossible but they rely heavily on radar, which is easy to find once they turn it on, and the AAA guns aren't much use against cruise missiles, stealth aircraft, or other standoff weapons.