Bank of China (BOC) , the country's fourth-largest lender by market value, on Thursday posted a net profit of 45.4 billion yuan ($7.28 billion) in the first quarter as net interest margins widened and its capital ratio improved.

The bank's net profit grew by a 13.9 percent from last year, and its total capital adequacy rose sharply to 12.95 percent, compared to 12.46 percent at end-December last year.