"The federal government is dealing with the case, and all the appropriate public authorities are participating intensively," a foreign ministry spokeswoman said.

More than 20 ships from the EU, Nato, China and Russia now patrol the waters off Somalia and around the Horn of Africa, a busy shipping lane plagued by pirates.

Shipping routes off the coasts of eastern and western Africa have become increasingly dangerous.

Dozens of ships seized by pirates have been released after owners paid tens of millions of dollars in ransom.