Global pirate attacks rose by 38.5% in 2009, according to the International Maritime Bureau.
The Kuala Lumpur-based body said of the 406 maritime incidents reported in 2009, suspected Somali pirates accounted for more than half.
In the Gulf of Aden 116 actual and attempted attacks have taken place, compared to 92 in 2008.
Somali pirates were held responsible for 217 acts of piracy in 2009, the report said.
As of 31 December, suspected Somali pirates have held 12 vessels for ransom and taken 263 crew hostages of various nationalities.