Large Chinese state banks intervened in the offshore renminbi forwards market in recent days to ease depreciation pressure by raising the cost to investors of betting that the currency will weaken.
A trader told the Financial Times that state banks had bought offshore renminbi forwards since Monday in what appeared to be a concerted, if modest, action. This activity has the effect of tightening offshore renminbi liquidity, raising the cost of borrowing the currency in order to place short bets.
Large state banks acting together are typically viewed as doing so on behalf of the central bank. The People's Bank of China has previously acted to tighten offshore renminbi through both explicit policy and undeclared intervention through state banks.