BEIJING — Yields on short-term Chinese government bonds are on the rise, even after two cuts to a key interest rate, as tightening capital supply undermines the central bank’s efforts to boost the economy by stimulating demand.

The People’s Bank of China, the country’s central bank, lowered the one-year loan prime rate, its key policy rate, in June and August, taking a step that often pushes down yields on many financial instruments, including government bonds.