Oslo  - The fund that invests income from Norway's petroleum and gas riches for future pensions has been impacted by recent global financial turmoil, registering its weakest quarter to date, the central bank said Friday.

The return on the fund during the first quarter 2008 fell by 5.6 per cent measured in international currency, the bank said.

The Norwegian Government Pension Fund - Global was worth 1.946 billion kroner (390 billion dollars) at the end of the first quarter, compared to 2,019 billion kroner at the end of 2007.

"The results for the first quarter reflect ongoing financial unrest," central bank governor Svein Gjedrem said.

Factors the central bank listed included the continued fall-out from the US mortgage market that has impacted stock markets around the world, and the slowdown in the US.

The fund, managed by the central bank, was approved in 1990 by parliament.

It was created to pay for Norway's future health and pension expenditure through investments outside the Norwegian economy.

The capital is invested in bonds, shares, money market instruments and derivatives. (dpa)