A French warship has thwarted an attack by Somali pirates on a cargo ship in the Gulf of Aden and arrested eight men, the French military says.

Christophe Prazuck, a spokesman for the French armed forces, said on Friday that the pirates fled after the frigate first approached and were eventually captured when they made a second attempt to seize the S Venus some hours later.

"Resistance was impossible when faced by a well-armed warship," Prazuck told LCI television, adding that the French forces had found a rocket launcher, assault rifles and boarding ladders on the pirate's vessel.

The operation happened some 80km from the coast of Yemen and the eight men seized by the French will be taken to nearby Somalia for trial.

"There is a diplomatic agreement whereby the Somali authorities are committed to prosecuting and punishing [pirates]," Prazuck said.

Menace

Piracy off Somalia, one of the world's busiest shipping areas, has soared over the past year, earning the pirates millions of dollars of ransom payments and pushing up maritime insurance rates.

In a bid to deter the bandits, the European Union set up an anti-piracy naval task force under British command last month involving warships and aircraft from several nations in the first such naval operation of its kind.

France has been particularly active in the fight and has arrested 29 pirates in four operations since last April.

Besides the European Union, other nations like India and Malaysia have also sent navy ships to patrol the Gulf of Aden and the Indian Ocean to protect cargo vessels.

However, not all pirate activity has stopped.

Two ships were hijacked in December 2008. On Thursday, Egyptian officials said a cargo ship - Blue Star - carrying 6,000 tonnes of fertiliser was seized by pirates.