Berlin  - The German navy detained nine people Tuesday following a dramatic action to head off a pirate attack on a German merchant vessel off the coast of Somalia.

A tricky deliberation process has started in Germany, which has to decide how to legally proceed with the pirates.

This is the first time in the history of modern Germany's navy that anyone has been apprehended at sea.

According to German Defence Ministry in Berlin, a vessel owned by a Bremen-based shipping company, the MV Courier, was attacked by pirates during early morning Tuesday.

The ministry said that the pirates were armed with anti-tank rocket launchers and firearms.

US Navy helicopters thwarted the attack with soldiers of the German frigate Rheinland-Pfalz a short time later, seizing the pirate's boat and arresting nine people, the Defence Ministry said.

Some of the pirates were from Sudan, the ministry said.

The German sailors encountered a sizeable weapons stash, which they threw overboard for security reasons, according to Defence Minister Franz Josef Jung.

Germany must now decide how to proceed with the men, and whether to try them in Germany or hand them over to another country. Basic medical checks were carried out on them, on board the Rheinland- Pfalz.

Now it needs to be established whether German interests are at stake, in which case the country's legal system can swing into action.

A specially convened commission, including the Interior, Foreign, Defence and Justice Ministries, is expected to decide Wednesday whether to proceed under German law.

If this is the case, the pirates would initially be taken to Djibouti, where the European Union's (EU) anti-pirate mission is based. From there, German federal police agents would collect the men and transfer them to Hamburg.

The legal status is further complicated by the fact that the ship, although registered in the German city of Bremen, was sailing under an Antiguan flag.

The German navy joined the EU's anti-pirate mission Atalanta at the end of 2008 with what Jung described then as a "robust mandate."

In 2008, pirates seized more than 200 ships off the Somali coast, demanding millions of dollars in ransom. (dpa)