The BOJ buys 90 billion yen (559 million pounds) of REITs annually as a part of its stimulus programme. In spite of more than three years of aggressive easing, however, the central bank has not reached its inflation target of two percent and economic growth has hardly accelerated.

As its REITs portfolio kept expanding, the BOJ scrapped its long-held rule to limit ownership of each REIT to within five percent in December, a move opposed by three of its nine board members.

In the following month, the BOJ took additional easing steps by introducing negative interest rates.

After three years of massive asset purchases by the BOJ, Japanese markets have become increasingly dominated by the central bank.

The BOJ is also thought to own more than five percent of many listed Japanese shares through its buying of exchange traded funds (ETFs) though its holdings are not made public because the central bank is not buying shares directly.

(Reporting by Hideyuki Sano and Hirotoshi Sugiyama; Editing by Jacqueline Wong)