The Bank of Japan says its government bond holdings expanded to a record level by the close of the fiscal year on March 31. The central bank has been buying up the bonds for years as part of a monetary easing project that it is now starting to unwind.

The BOJ says it had 589.6-trillion-yen worth of government bonds on the final day of the fiscal year. That's nearly 3.9 trillion dollars. It's an increase of 1.3 percent in yen terms from a year ago.

The central bank's ETF holdings, also at a record high, amounted to 37.1 trillion yen, or nearly 250 billion dollars.

The bank said last month it was pivoting away from its easy money project and would raise its key rate out of negative territory for the first time in years. It said it would continue to buy JGBs at broadly the same rate but would halt purchases of new ETFs.

The BOJ Governor Ueda Kazuo told a Diet committee meeting on Friday: "In the future, we want to move forward with the exit from our massive monetary easing program. We want to start by dialing back new bond purchases and eventually we hope to reduce the bank's holdings."

Ueda also said he has no plans to start selling off the bank's ETF holdings in the near future.