Armed pirates have hijacked a merchant ship off the coast of Somalia, holding 20 of its crew hostage, an ocean crime watchdog says. The attacks, one on a United Arab Emirates (UAE) general cargo ship on Sunday and another launched from a so-called "mother ship" last Friday, come only days after a US Navy warship captured a band of suspected pirates with a cache of arms. Jayant Abhyankar, deputy director of the International Maritime Bureau (IMB), told Reuters on Wednesday: "With these attacks we now have a grand total of five ships and around 100 mariners being held hostage in Somalia, it was as many as 200, and some have been held for four months." The IMB said gunmen stormed the UAE-owned Al-Manara 150 nautical miles off the east coast of Somalia, threatened the crew, and are now demanding a ransom for their release.