China's five biggest banks have reported record net profits for 2011 due to higher net income margins and fee incomes.

Net profits at the banks, including the Industrial and Commercial Bank of China (ICBC), China Construction Bank (CCB) and Bank of China (BOC), surged to 680.85 billion yuan (108.07 billion U.S. dollars) last year, roughly equal to incomes of 1.87 billion yuan per day, according to statements filed to the Shanghai Stock Exchange.

ICBC, the country's largest lender, fared best last year, with profits increasing 25.6 percent to 208.44 billion yuan, followed by CCB with 169.44 billion yuan and Agricultural Bank of China with 121.96 billion yuan.

The BOC said its 2011 net profits rose to 124.18 billion yuan, up 18.93 percent, while the Bank of Communications saw profits jump nearly 30 percent to 50.74 billion yuan.

The lenders attributed their profit gains to rising net interest income and revenues from fee-based services and commissions.

China's banking regulators have launched a nationwide campaign against unnecessary fees, as public criticism has been mounting over the proliferation of fees charged by banks.

Banks may find it difficult to increase their interest margins this year, as demand for loans will likely soften amid a slowing economy, analysts said.

"Interest margins will stabilize or fall slightly this year, while banks' profit growth will likely sink below 20 percent," said Jin Lin, an analyst at Orient Securities.