Nicolai Tangen said his COVID-19 test, taken on Wednesday, had come up as positive but that he did not know how he contracted the coronavirus.

"This means that I am now isolated in my apartment in Oslo where I will be working from for the next couple of weeks," he wrote in a post on his LinkedIn account.

"My symptoms are mild," he said.

Tangen added that a number of his colleagues at the fund, which has its offices in central Oslo, had been quarantined as a result of his positive COVID-19 test.

"Reports so far are that they all feel ok," Tangen said.

The Norwegian fund, the world's largest sovereign wealth fund, is managed by a unit of the central bank. Central Bank governor Oeystein Olsen is one of Tangen's colleagues who is now in quarantine, a Norges Bank spokesman said.

Norway's central bank hired Tangen this year to manage Norges Bank Investment Management (NBIM), which runs the fund which owns 1.5% of globally listed stocks and vast portfolios of bonds and real estate.

Tangen took the helm at the fund on Sept. 1, replacing Yngve Slyngstad, who stepped down after 12 years as the fund's CEO.

Norway's capital Oslo imposed a "social lockdown" to stem the spread of COVID-19 on Nov. 6, shutting theatres, cinemas, training centres and swimming pools, and also banning the sale of alcohol at bars and restaurants.

(Additional reporting by Terje Solsvik; Editing by Edmund Blair, Larry King and Pravin Char)

By Victoria Klesty