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No details were published about the scale of the operation, or which banks had been involved, but the liquidity injection evoked memories of the crisis measures taken by central banks in Europe and the US in the wake of the collapse of Lehman Brothers, as markets threatened to dry up altogether.

While markets in much of the world have been fixated on the Federal Reserve's decision to being tapering its quantitative easing programme, China's relatively closed markets mean it has so far felt little impact from the announcement late on Wednesday. "China's financial system is by and large walled off from the rest of the world," said Williams.

Lorraine Tan, director of equity research at S&P Capital IQ, told CNCBC that the PBoC may need to take more action.

"I think it's just a momentary thing … it's a seasonal issue, a rush for cash. Definitely the PBoC needs to pump in more money, which it has been doing, but a little bit more is probably necessary."