AVERAGE rents of prime office space rose for the first time since the third quarter of 2011, with more tenants looking for top office spaces.

The average rents of prime Grade A+ office space in Marina Bay and Raffles Place increased 1.4 per cent in the third quarter, from the previous quarter.

Gross effective monthly rentals for Grade A+ office space are between $9.90 and $12 this quarter, which comes after seven consecutive quarters of negative or flat growth, said Knight Frank's latest quarterly research report on Sept 16.

This comes after a quiet period after the mid-year holiday season, as leasing activity grew in the third quarter while firms anticipate recovery in office rents.