Berlin  - A German warship carrying seven pirates detained off the coast of Somalia arrived in the Kenyan port of Mombasa on Wednesday, German naval officials said.

The Somalis were picked up by the frigate Rheinland-Pfalz after they carried out an abortive attack on a German naval tanker in the Gulf of Aden last month.

When the frigate docked it was unclear whether the pirates would be handed over to Kenyan authorities or flown back to Germany for prosecution.

A court in the German city of Kiel issued arrest warrants for the seven on Wednesday.

Under a deal with the European Union, Kenya has pledged to try pirates detained by EU warships for attacks on merchant shipping off the Somalia coast.

It is unclear whether the arrangement applies to attacks on navy ships.

On March 9, Germany handed over to Kenya nine pirates captured off Somalia after another botched attack, this time on a German freighter.

Piracy has started to pick up again off Somalia in recent weeks following a lull of several months.

On Wednesday, a Danish-owned container ship with 21 American crew on board was seized in the Indian Ocean.

Pirates in 2008 captured dozens of ships and earned tens of millions of dollars in ransom, prompting the international community to send in warships to the region.(dpa)