Grade-A office rents in Beijing remained unchanged in the first quarter while the vacancy rate edged up for two straight quarters, a report from international real estate specialists Knight Frank showed.

The average monthly rent for Beijing's grade-A offices remained unchanged at 396 yuan ($63.9) per sq meter in the first quarter. The market vacancy rate increased by 1 percentage point to 4.8 percent.

The small amount of new supply means a further increase is unlikely, according to the report.

Zhang Jingjing, senior manager of Research & Consultancy at Knight Frank Beijing, expects the number of Beijing's grade-A offices to increase slightly in 2013 compared with 2012.

Due to further stringent control on the residential market in Beijing, some investors may shift to the commercial market.

Meanwhile, due to stagnant rental growth, capital yields in the office market are expected to decline, said Zhang.