Tokyo office vacancies fell in January, nearing a seven-year low, after rising in December for the first time in six months, real estate brokerage Miki Shoji Co. said Thursday.

The vacancy rate in the five central wards dropped in January to 2.55 percent, from 2.65 percent in December, Miki Shoji said in a report released through the Land, Infrastructure and Transportation Ministry. Vacancies fell to 2.49 percent in November, the lowest since at least 2001, when Miki Shoji began compiling monthly data.

A lack of Grade A office buildings is pushing up rents even as economic growth slows. Developers and landlords are expected to add 220,000 "tsubo" (726,000 sq. meters) of new space this year, about half as much as hit the market in 2006, according to Miki Shoji.

"Demand is very strong," said Daisuke Seki, chief executive officer of Tokyo-based IB Research and Consulting Inc. "It's a landlord's market."

There is almost no space free in Tokyo, as some offices registered as vacant represent space that is slated for renovation, Seki said.

Office rents in the five main business districts in Chiyoda, Chuo, Minato, Shinjuku and Shibuya wards rose to ¥22,452 per tsubo in January, from ¥21,998 the previous month.