Qatar has accumulated a small stake in Siemens, Germany's most valuable company, worth roughly 2.4 billion euros ($3.08 billion), adding to the natural gas-rich country's portfolio of minority investments around the world.

In a regulatory filing published on Tuesday, the German industrial group said that a subsidiary of the state-owned Doha Insurance Company (DIC) had exceeded the 3 per cent threshold in voting shares on May 7, which triggered the mandatory disclosure.

The Gulf nation's immense supply of natural gas has made it so rich, that it has been snapping up assets at a breakneck pace as it struggles to find enough attractive investment opportunities to keep up with its constantly growing cash pile.

As a result, Qatar has been the most active of the Gulf region's sovereign investors in recent years, buying stakes in companies including Credit Suisse, Barclays, Agricultural Bank of China, Santander Brasil  as well as London's famed Harrods department store.

Alone in Germany it controls a 17 per cent voting stake in Volkswagen and one-tenth of the unlisted common shares in automotive holding Porsche SE. The state also owns a holding in construction group Hochtief.

Last week, sovereign wealth fund Qatar Investment Authority (QIA) bought a stake in Royal Dutch Shell, and earlier reports said that it was looking at a 3-5 percent stake.-Reuters