Fifteen incidents were reported off Somalia in 2013, down from 75 in 2012 and 237 in 2011, the International Chamber of Commerce's International Maritime Bureau annual report indicated Wednesday.
"The single biggest reason for the drop in worldwide piracy is the decrease in Somali piracy off the coast of East Africa," said Capt. Pottengal Mukundan, director of the IMB, whose Piracy Reporting Center has monitored world piracy since 1991.
The bureau said Somali pirates have been deterred by several factors, including international navies, the hardening of vessels, the use of private armed security teams and the stabilizing influence of Somalia's central government.
"It is imperative to continue combined international efforts to tackle Somali piracy. Any complacency at this stage could re-kindle pirate activity," Mukundan said.
The 15 incidents attributed to Somali pirates last year included two hijacked vessels, both released within a day because of naval actions, and eight vessels that were fired upon, the report said.
The number of incidents is the lowest since 2006, when 10 Somali attacks were recorded, the bureau said.
West African piracy made up 19 percent of attacks worldwide last year, the report said, responsible for 31 of the region's 51 attacks, taking 49 people hostage and kidnapping 36, more than in any year since 2008.
In Indonesian ports and waters, the IMB report said there were a high number of "low-level opportunistic thefts" that shouldn't be compared to the "more serious incidents off Africa."