Pirates kidnap five crew from ship off Nigeria ABUJA (Reuters) - Pirates have kidnapped five crew members from a cargo ship off Nigeria, the vessel's management company said on Monday, part of a growing trend of attacks that are pushing up maritime insurance costs in the Gulf of Guinea. A Russian and a Polish citizen were among those taken hostage when the Antigua and Barbuda-flagged MV City of Xiamen container ship was attacked late on April 25 about 100 miles off Nigeria's coast, Sunship Schiffahrtskontor KG, the ship's German operator, said in a statement. The International Maritime Bureau (IMB) said 14 heavily armed pirates attacked the container ship, breaching its citadel - a strong room designed to protect the crew from attack. They took five crew captive before escaping with cash taken from the ship and the crew, the IMB said in a piracy report. Pirates in a speed boat off Nigeria chased and fired upon another container ship on April 24 but the vessel increased speed and escaped, the IMB said. West Africa is an important source of oil, cocoa and metals for world markets, but international navies are not engaged in counter-piracy missions at present. Many vessels anchor off Nigeria with little protection, making them a soft target for criminals. Naval patrols and the presence of armed guards aboard merchant vessels have helped reduce piracy off Somalia on Africa's eastern coast. Reporting by Joe Brock; Additional reporting by Gabriela Baczynska in Moscow; Editing by Tim Cocks and Jon Boyle