SHANGHAI, Jan 15 (Reuters) - China stocks fell on Monday, after the country's central bank surprised markets by leaving the interest rate unchanged when rolling over maturing medium-term policy loans.

The People's Bank of China (PBOC) instead boosted liquidity injections in the operation. It kept the rate of medium-term lending facility (MLF) loans unchanged at 2.50% but injected a net 216 billion yuan of fresh fund into the banking system.

China's CSI 300 index was down 0.5%, while the Hang Seng benchmark lost 0.7% in early trade.

In a Reuters poll of 35 market participants conducted last week, 19, or 54.3%, had expected the central bank to cut the MLF rate to help shore up the weak economy.

Real estate developers fell roughly 1.5% to lead the decline, and new energy shares were down 1%. Hong Kong-listed tech giants declined roughly 2%. (Reporting by Shanghai Newsroom; Editing by Subhranshu Sahu)