A building in Singapore going to be bought by a Qatar sovereign wealth fund is apparently the largest single-tower real estate being sold in entire Asia Pacific.

Asia Square Tower 1, owned by BlackRock and located along Marina View at Marina Bay is going to the hands of Qatar Investment Authority for S$3.4bn.

The 43-storey Asia Tower 1 has more than 1.25 million square feet of net lettable area and has Citigroup as its anchor tenant, BlackRock and Qatar Investment Authority said in a joint statement, according to a Reuters report.

BlackRock was advised by real estate consultant firms JLL and CBRE.

"Following this flagship transaction, we expect there will be increasing investor interest in Singapore prime office stock in the coming months," Greg Hyland, head of capital markets Singapore at JLL, said in a separate statement.

The sale is not happening in good times for Singapore commercial realty as vacancy rates in the City's office property sector are nearing their highest level in almost a decade.

The supply of commercial space is set to increase amid slowing economic growth, analysts said.

Developers are set to add 4 million square feet of office space in Singapore this year and another 1.4 million next year, said Nicholas Mak, executive director at SLP International Property Consultants.

BlackRock also owns a second tower in the Asia Square development.