China's economy slowed further in October, according to data from its National Bureau of Statistics, signaling that policymakers' piecemeal stimulus is failing to boost output and investment amid ongoing trade tensions with the U.S. and subdued demand at home.

Investment grew at the slowest pace since at least 1998, that data shows, with private companies pulling back. Industrial output and retail sales growth also slowed more than expected, showing that demand continues to weaken right across the economy.

The data, released Thursday, forms further evidence that policymakers' efforts to brake the slowdown are falling behind the curve as the nation faces structural downward forces at home and uncertainty clouding its trade outlook with the U.S.