Nato said a Portuguese warship went to the rescue of the MV Kition after the Norwegian crude oil tanker radioed for help on Friday afternoon as a skiff full of pirates brandishing assault rifles and rocket-propelled grenades approached . " We were the nearest warship , so we immediately scrambled our helicopter , " said Nato Lieutenant Commander Alexandre Fernandes from the Corte-Real , which was about 20 nautical miles north of the tanker when the distress call went out .