Commercial real estate firm CB Richard Ellis said office tenants vacated 34,255 square feet of space on O'ahu in the third quarter, though occupancy is still up by 20,428 square feet for the first nine months of the year.

The company said O'ahu's office vacancy rate is 9.3 percent, or nearly 1.1 million square feet, up from 8.2 percent, or 950,000 square feet, at mid-year.

CB Richard Ellis said landlords are responding to economic weakness by being more aggressive with deals that include free rent periods in trying to keep tenants when leases come up for renewal. But landlords also are asking for higher rent to compensate for increased operating expenses that include electricity. The average monthly gross asking rent per square foot of space has risen 15 cents over the last 12 months to $2.99.

The CB Richard Ellis occupancy figures are based on a survey of 101 buildings in the two highest classes of property. Lower quality office buildings known as Class C buildings are not included in the survey.