The MV Amani, owned by Yemeni shipping firm Abu Talal, has seven sailors on board.

It was seized on November 25 as it carried 507 tonnes of steel from Yemen's Mukalla port to Socotra Island.

There have been nearly 100 attacks in Somali waters this year, despite the presence of several foreign warships.

The sea gangs have received tens of millions of dollars and are still holding about a dozen ships and nearly 300 crew.

UN clearance

The United Nations Security Council has renewed its authorisation for the use of military force against pirates operating off Somalia, enabling the European Union to begin an air and naval operation next week.

"The international community is sending a very strong signal of its determination to deal with piracy," said Jean-Maurice Ripert, the French ambassador to the UN.

The EU is set to send warships to patrol Somalia's Gulf of Aden and the Indian Ocean waters, where a rise in piracy is threatening to stifle one of the world's busiest maritime trade routes.

"We think it will act both as a deterrent and also [provide] some immediate capacity to follow on and pursue pirates, if we can catch them," Ripert said.

But the issue of who has jurisdiction over captured pirates and where they can be prosecuted remains unresolved.

Naval operations

The European mission is aimed at protecting ships that carry World Food Programme supplies to feed about three million Somalis who depend on food aid, as well as escorting shipping frigates in the area.

The naval force, backed by patrolling aircraft, will be commanded by British forces.

There are already several international naval operations along the Horn of Africa, including a Nato mission to counter piracy, but they have done little to deter hijackers, who have been paid tens of millions of dollars in ransoms by firms seeking to free hijacked ships.

The US-drafted resolution, which was adopted unanimously, extends for one year the right of countries with permission from Somalia's transitional government to pursue and attack pirates in Somali waters.