Norway's vast oil fund has made its first real estate investment in the U.S., buying stakes in five office buildings in New York, Washington and Boston for $600 million.

The Norwegian central bank, which manages the $650 billion fund, says it bought 49.9 percent of the properties in a joint venture with New York-based financial services firm TIAA-CREF.

The bank says the joint venture aims to acquire additional U.S. office buildings, primarily in those three cities. The Norwegian fund has previously invested in real estate in London and Paris.

Norway, a small country made wealthy by its offshore oil and gas resources, sets aside surplus government revenue in the oil fund - officially called the Government Pension Fund Global - for foreign investment to avoid overheating the domestic economy.