Japanese property giant Daibiru is in due diligence to buy a $600 million Sydney office tower, amid signs of resurging interest in the most battered corner of the commercial real estate market.

The mooted deal, if completed as expected, would bring the tally of office towers sold in Sydney’s financial core this year to more than $4 billion. Colliers’ head of office capital markets, Adam Woodward, said that volume of deals for Sydney’s core is greater than the previous four years combined.