China’s property prices rose at the fastest pace in 18 months in December, highlighting the government’s struggle to rein in speculation while maintaining economic growth.

Residential and commercial real-estate prices in 70 cities climbed 7.8% from a year earlier, the National Development and Reform Commission said on its Web site today. That topped a 5.7% gain in November.

The increases signal the risk that asset bubbles may hamper the recovery of the world’s fastest-growing major economy and stoke discontent among workers unable to afford homes.