Bank of Tokyo-Mitsubishi UFJ on Thursday became the first Japanese bank to take an equity stake in a Chinese bank, purchasing $180 million in Bank of China shares as it listed on the Hong Kong Stock Exchange the same day.

Investing in Bank of China, one of China's four biggest state-owned commercial banks, is a step toward reinforcing BTMU's operations in China, officials at BTMU said Wednesday.

The Japanese bank acquired a stake of around 0.2 percent in the Beijing-based bank as it went public.

BTMU currently has five branches in China and plans to increase the number to around 10. But as a rapid expansion of its branch network is difficult because of the time-consuming procedures required for approval by Chinese authorities, the commercial bank decided to expand its presence in China through Bank of China.

Specifically, BTMU hopes to expand loans to Japanese companies operating in China. The Tokyo-based bank also intends to launch retail banking services in China.

While Chinese banks have been accepting capital contributions from major European and U.S. banks, Japanese banks have lagged behind in developing the Chinese market.