A US warship has captured five suspected pirates after an exchange of fire in the Indian Ocean west of the Seychelles, the US navy said.

"USS Nicholas captured suspected pirates on Thursday after exchanging fire, sinking a skiff, and confiscating a suspected mothership," the US Navy said in a statement.

After the clash, the US ship chased the suspected pirate ship, which had been damaged, until it stopped, it said, capturing three pirates on the skiff and another two on the mothership.

The US said that it expected pirates to increase attacks on merchant vessels due to better weather from March through to May.

Pirates operating off Somalia have stepped up hijack attacks on vessels in the Indian Ocean and the Gulf of Aden in recent months, making tens of millions of dollars in ransoms, despite the presence of foreign navies off the coast of Somalia.

Attacks had created a two-year boom for specialist insurance cover, but stiff competition and moves by owners to better protect ships have taken the edge out of insurance costs.

Maritime assaults

Pirate sources said a Taiwanese ship had also been hijacked on Thursday, while a Turkish frigate intercepted a skiff in the Gulf of Aden and captured nine Somali pirates who were suspected of preparing to attack ships, the Turkish military said on Thursday.

The Gelibolu, operating with Nato forces in the region, spotted the skiff on Wednesday, about 130km off the shore in a transit corridor commercial vessels are encouraged to use for safe passage.

Commandoes seized the vessel, along with equipment used in piracy operations, the Turkish military said in a statement online.

A photograph posted on the army's website showed the suspected pirates holding their hands up in surrender.

Since January, Somali pirates have attacked 32 ships, seven of which were hijacked, the International Maritime Bureau (IMB) piracy reporting centre said on Thursday.

Pirates were holding eight ships in total and 143 crewmen of different nationalities, it added.