OSLO: Norway’s central bank said on Thursday it would buy foreign currency for its sovereign wealth fund in April, the first time it has done so in almost nine years, amid a surge in the country’s oil and gas revenues, weakening the crown currency.

Norges Bank plans to exchange 2 billion crowns ($231.9 million) per day into foreign currency, which will in turn be invested abroad by the wealth fund, already the world’s largest with assets of $1.3 trillion.

A spike in the price of petroleum, Norway’s main export, has led to a big inflow of tax revenue that exceeded government spending.

Economists have said a switch to buying foreign exchange, and thus selling crowns, may weaken the currency.