(CNN) -- Pirates have seized a tanker ship in the Indian Ocean and appear to be taking it to Somalia, the European Union Naval Force Somalia said Monday.
Pirates boarded the MV Jubba XX on July 16 as the ship traveled between the United Arab Emirates and Berbera, Somalia, according to a task force statement.
A patrol plane spotted the ship on Sunday headed for northern Somalia. The task force said it believes nine pirates are aboard the ship, which has a crew of 16. No information about their condition was available.
The ship was not registered with the Maritime Security Centre - Horn of Africa, which provides 24-hour tracking of vessels traveling through the pirate-infested area, the agency said.
Somali pirates have attacked merchant vessels 163 times in the first six months of 2011, up 63 percent over the same period in 2010, according to the International Maritime Bureau's Piracy Reporting Centre. Twenty-one of those attacks resulted in successful hijackings, the organization said.
Somali pirates were holding 20 vessels and 420 crew members as of June 30, the group said.