Investors are pushing commercial real-estate prices to record levels in cities around the world, fueling concerns that the global property market is overheating.

The valuations of office buildings sold in London, Hong Kong, Osaka and Chicago hit record highs in the second quarter of this year, on a price per square foot basis, and reached post-2009 highs in New York, Los Angeles, Berlin and Sydney, according to industry tracker Real Capital Analytics.

Deal activity is soaring as well. The value of U.S. commercial real-estate transactions in the first half of 2015 jumped 36% from a year earlier to $225.1 billion, ahead of the pace set in 2006, according to Real Capital. In Europe, transaction values shot up 37% to €135 billion ($148 billion), the strongest start to a year since 2007.

Low interest rates and a flood of cash being pumped into economies by central banks have made commercial real estate look attractive compared with bonds and other assets. Big U.S. investors have bulked up their real-estate holdings, just as buyers from Asia and the Middle East have become more regular fixtures in the market.

The surging demand for commercial property has drawn comparisons to the delirious boom of the mid-2000s, which ended in busts that sunk developers from Florida to Ireland. The recovery, which started in 2010, has gained considerable strength in the past year, with growth accelerating at a potentially worrisome rate, analysts said.