A German Navy warship sank two empty speedboats belonging to Somali pirates, but let their mother ship go Friday for fear of hurting hostages, dpa cited the armed forces command in Berlin as saying. The frigate Niedersachsen discovered the pirate ship Jelbut 31 in the Indian Ocean off the coast of Tanzania. The frigate's helicopter observed bazookas on the big vessel. But the pirates were "uncooperative and aggressive" when the Germans asked them by radio to stop. With permission from the European Union anti-piracy Operation Atalanta, the Germans decided to destroy the two speedboats in tow behind the Jelbut 31, and shot them up with the Niedersachsen's guns and the helicopter's cannon after making sure they were empty. Sources said the Navy decided not to capture the mother ship because there were hostages including women and children on board, and a firefight during an armed boarding might have endangered their lives. The pirates asked the frigate by radio to stop shooting so the shattered speedboats could be cut adrift. After the pirates cut the lines, the boats were sunk completely by the Germans. Germany joined the EU naval operation in 2008.