Office vacancies in Tokyo's five key wards rose 0.67 point to 5.60 percent in February, topping the boom-or-bust line of 5 percent for the first time since July 2005, office broker Miki Shoji Co. said Thursday.

The rate in the wards of Chiyoda, Chuo, Minato, Shinjuku and Shibuya has soared for 13 consecutive months as companies accelerate consolidation efforts amid rapidly deteriorating economic conditions.

While real estate prices have generally slackened, demand for excellent offices was believed to be steady in central Tokyo. But not anymore. "Even central Tokyo is no longer safe," a Miki Shoji official said.