Japan has sent two navy destroyers to the water's off Somalia's coast to join international anti-piracy efforts in the region.
The ships carry helicopters and speedboats and a combined crew of 400.
A day earlier, on Friday, South Korea sent a warship to join the anti-piracy force.
The International Maritime Bureau says international anti-piracy efforts have reduced the number of successful hijackings in the area to one in seven attacks.
Somalia-based pirates carried out more than 120 attacks on ships last year, hijacking 42. In some cases, the pirates received millions of dollars in ransom for the release of the ships.
NATO, the European Union, China and the United States are among naval powers with warships on patrol off Somalia.
Japan sent the destroyers after its Cabinet approved use of the country's self-defense forces to protect Japanese-flagged ships and Japanese citizens. Japan's post-World War II pacifist constitution limits its military to defensive operations.
Some information for this report was provided by AFP, AP and Reuters.
