Kidnappings at sea and hijackings by armed pirates in the Gulf of Guinea have increased in the first half of 2013.
A wider range of ship types are being targeted, according to a global piracy report by the International Chamber of Commerce's (ICC) International Maritime Bureau (IMB).
So far this year around 31 incidents have been recorded, including four hijackings and 56 sailors taken hostage.
By contrast, the report revealed that Somali piracy has fallen to its lowest levels since 2006, with eight piracy incidents reported during the first half of 2013 in East Africa's Gulf of Aden and Somalia.
IMB Piracy Reporting Centre recorded 138 piracy incidents across the world compared to 177 during the first half of 2012. Seven hijackings were recorded during the period compared to 20 for the same period last year, while the number of sailors taken hostage also decreased from 334 to 127.
IMB director Pottengal Mukundan said that there has been a worrying trend in the kidnapping of crew from vessels well outside the territorial limits of coastal states in the Gulf of Guinea.
"In April, nine crew members were kidnapped from two container vessels, one of which was 170 nautical miles from the coast," he said.
"Pirates have used motherships, some of which were smaller off-shore supply vessels hijacked by pirates to conduct the attacks."
In June, a group of 22 West and Central African nations agreed to establish a regional centre for coordinating the fight against piracy in the Gulf of Guinea, which is affecting international navigation, security and the economic development of the region.
The regional centre will help in sharing and reporting information and operational coordination mechanisms in the region, as well as build on existing initiatives, such as those under the support of the International Maritime Organization.
According to the IMB's report, pirate attacks off the coast of West Africa's Gulf of Guinea almost doubled in 2012, with attacks in the region numbering higher than those in the waters around Somalia.
In 2012, around 966 sailors were attacked in West Africa, compared to 851 attacked off the Somali coast.
Image: In the first half of 2013, pirates in the Gulf of Guinea took 56 sailors hostage. Photo: Commercial Crime Services, a division of the ICC.