BEIJING, April 18 -- The central bank pumped 162.5 billion yuan (about 25 billion U.S. dollars) into the financial system on Monday in open market operations via medium-term lending facility (MLF).

MLF is a tool introduced in 2014 to help commercial and policy banks maintain liquidity by allowing them to borrow from the central bank by using securities as collateral.

The fresh funds were injected into 18 financial institutions, according to the People's Bank of China (PBOC).

A total of 83.5 billion yuan is for three-month MLF and 79 billion yuan is for six-month MLF, at interest rates of 2.75 percent and 2.85 percent, respectively.

The interest rates were left unchanged to "guide financial institutions to boost support for key areas and vulnerable links in the national economy," the central bank said.

To bolster the lukewarm economy, China has adopted a more pro-growth policy stance, cutting benchmark interest rates and banks' reserve requirement ratio (RRR) multiple times since 2014.

The country's GDP grew 6.7 percent year on year to reach 15.9 trillion yuan in the first quarter, according to the National Bureau of Statistics (NBS).

The growth further narrowed from the previous quarter's 6.8 percent, which was already the lowest quarterly rate since the global financial crisis.