Recent satellite images show two new North Korean frigates, the largest surface combat ships the nation’s navy has constructed in a quarter-century, a North Korea-watching website reported Thursday. The website, 38 North, says the frigates are designed to carry one helicopter each and appear to be designed to counter South Korean submarines and protect fisheries. The vessels appear to be equipped with anti-submarine rocket launchers. The vessels can be seen in commercial satellite images from December and January. One is berthed at a shipyard in the west coast port of Nampo, other at a shipyard at the northeastern port of Nanjin. More