China's "big four" state-owned commercial banks are getting into full swing as their interest income continues expanding.

Industrial and Commercial Bank of China (ICBC), the country's top lender by assets, said first-quarter profits soared 29 percent from the previous year to reach 53.84 billion yuan ($8.3 billion).

The bank's net interest income, which reflects the difference in revenue from lending and the cost of deposits, surged 25 percent to 85.4 billion yuan ($13.1 billion) in the January-to-March period. Net fee and commission income from products and services such as credit cards, wealth management and insurance sales rose 42 percent to 25.9 billion yuan ($4 billion).

China Construction Bank, the second largest lender, saw its net profits climb 34.2 percent to 47.23 billion yuan ($7.3 billion).

Bank of China's first-quarter profits rose 28.03 percent to reach 35.01 billion yuan ($5.36 billion).

Agricultural Bank of China (ABC) generated 34.1 billion yuan ($5.2 billion) in net profits, up 36.4 percent.

In attempts to cool inflation, the central bank has twice raised interest rates and hiked the ratio of deposits that commercial banks must set aside in reserves four times this year. Despite those tightening measures, demand for credit remains buoyant as the economy picks up momentum, said Guo Tianyong, Director of the Research Center of China's Banking Industry at the Central University of Finance and Economics.

Jiang Jianqing, Chairman of ICBC, said the impact of rising interest rates on ICBC was largely neutral because any drop in borrowing demand was offset by higher income from interest margins.

The industry, however, was not without concerns. ICBC recorded a capital adequacy ratio of 11.7 percent by March, down 0.5 percentage points from the end of 2010. The ratio of ABC even dipped to 11.4 percent, below the government-set minimum requirement of 11.5 percent.