RABAT (Reuters) - At least 3 migrants, two of them women, died when their boat sank off Morocco late on Thursday, a Moroccan official said on Friday. Four migrants from sub-Saharan countries were rescued and were being treated in a Moroccan hospital, a hospital source who asked for anonymity said. A navy search operation for other possible survivors was underway, the official said. Another 28 people who were on their boat are still missing, Joel Millman, a spokesman for the U.N. International Organization for Migration said.  Millman said 174 people have already died on the route between North Africa and Spain this year, up from 121 in the same period of 2017, while the number of people arriving in Spain has reached 19,668 by Nov. 29. Morocco is, like other North African countries, a departure point for African migrants heading in makeshift boats for Europe.  