More Oahu office space was vacated than filled in the first three months of this year, extending a trend of rising vacancies to a fifth consecutive quarter, according to a new report.

A survey by local commercial real estate firm Colliers Monroe Friedlander said vacant space grew by 46,859 square feet in the January-March period, pushing the vacancy rate to 12.1 percent from 11.8 percent at the end of last year.

The first-quarter rate was the highest in nine years.

At 12.1 percent, the vacancy rate represents nearly 1.9 million square feet of empty space among roughly 15.7 million square feet at 161 large buildings surveyed by Colliers.

Most of the first-quarter increase in vacant space occurred in the Kalihi/Iwilei/Kapalama area. Downtown, Oahu’s largest submarket, saw vacancies decrease.

Base rents sought by landlords were unchanged, but electricity charges are rising as oil prices surge, Colliers said.

A separate report by another commercial real estate firm, CB Richard Ellis, said some signs of recovery are on the horizon, such as the absence of big blocks of office space being emptied by users.

“We enter 2011 with a guarded sense of optimism,” CBRE said in its report. “The worst is likely over from a property-level fundamentals perspective, although there is little doubt that the recovery process will be lengthy and difficult.”