SHANGHAI (Reuters) - China's central bank has questioned some banks on their demand for liquidity under its medium-term lending facility (MLF) and is expected to begin daily checks, two sources with direct knowledge of the issue told Reuters on Monday.

It also questioned some on Friday.

The bank kept the rates on offer unchanged from the last operation in May, at 2.75 percent for three-month loans and 2.85 percent for six-month loans, sources said.

The medium-term lending facility is a supplementary lending facility sometimes used by the central bank to adjust liquidity in the banking system.

The central bank did not have an immediate response when contacted by Reuters.

(Reporting by the Shanghai Newsroom; Editing by Simon Cameron-Moore)