“The actions of the navies in the Gulf of Aden have been instrumental in bringing down the attacks," said IMB director P. Mukundan in a report released by the bureau in a Reuters report.

Foreign navies have been deployed off the Gulf of Aden since the start of 2009 and have operated convoys, as well as set up and monitored a transit corridor for ships to pass through vulnerable points.

Pirates operating off the Somali coast have contributed to a spike in the number of attacks with the global total hitting a six-year high of 406 last year.

The bureau said attacks in the Gulf of Aden dropped 61 percent in the first half of this year to 33 incidents compared to 86 in 2009 but rose in the Somali basin and the wider Indian Ocean, from 44 attacks in 2009 to 51 this year.

The bureau said Somali pirates, who have hijacked 27 ships so far this year and took 544 crews hostage, are continuing to demonstrate an ability to attack at further distances.

"Some of these attacks have taken place more than 1,000 nautical miles from the Somali coast," said Mukundan.

The report said attacks in the South China Sea have more than doubled this year to 15 compared to 7 in the first half of 2009.

The bureau noted that attacks in the sea that links to the Malacca Straits, a key shipping lane for world trade, have ceased recently due to the Indonesian navy's increased presence.

"Although most of the incidents in Indonesian waters are low-level attacks carried out on vessels either at anchor or while carrying out cargo operations at berth, the risk to seafarers remains high," the bureau said.