Experts had warned in recent days that dropping winds near the Seychelles had attracted pirates.
Somali pirate gangs have made millions of dollars in ransom payments since last year and patrols by foreign navies in the Gulf of Aden have failed to end the problem.
The latest hijacking brings the number of vessels held by Somali pirates to at least six. The others include a Spanish trawler, a Taiwanese fishing vessel and Ukrainian, German and Turkish freighters.
According to non-governmental observers Ecoterra International, at least 163 attacks have been carried out by Somali pirates since the start of 2009. Forty-seven of them have been successful hijackings.
Nearly 20,000 ships pass through the Gulf of Aden each year, heading to and from the Suez Canal.