BlackRock, the world's largest asset manager, is exploring a sale of its second office tower in Singapore's central business district, people with knowledge of the matter said.

BlackRock has started reaching out to potential buyers to gauge their interest in Asia Square Tower 2, according to the people, who asked not to be identified as the information is private. The development could fetch about $2 billion.

Asia Square Tower 2 sits on the site next to Tower 1, which the Qatari sovereign wealth fund agreed to buy in June from BlackRock for $3.4 billion in Singapore's biggest office transaction.

Office transactions in Singapore have been picking up this year, with CapitaLand Commercial Trust agreeing in May to buy 60 per cent of CapitaGreen for $393 million.

Investment company MYP the next month said it plans to offer $560 million for the Straits Trading Building. The Government is also selling prime land in the Marina Bay financial district, the first such sale in nine years.

The increased deal activity is happening against the backdrop of rising supply and falling rents. Singapore's office vacancies rose to the highest in more than four years and rents slid 1.1 per cent in the quarter ended Sept 30.

Prices of office space decreased 0.4 per cent in the quarter, compared with a 1.5 per cent decline in the previous three months, according to data from the Urban Redevelopment Authority.

Competition among landlords is set to intensify as supply in premium and Grade A properties in the central business district expands, according to Colliers International.

Prime office rents in the central business district are expected to drop 7 per cent to 12 per cent this year, the broker said.

BLOOMBERG