Japanese stocks up after BOJ tweaks policy

The Nikkei swerved in and out of the red soon after the BOJ policy decision was announced and was last up more than 1 per cent.

The Nikkei has swerved in and out of the red since the BOJ policy decision was announced. (AAP)

Japanese stocks have rallied in volatile trade after the Bank of Japan's decision to modify its policy framework, which included an amendment to its purchases of exchange traded funds (ETFs).

The Nikkei swerved in and out of the red soon after the BOJ policy decision was announced and was last up more than 1 per cent, while the Topix gained 1.7 per cent after the central bank said 2.7 trillion of its ETF purchases will be linked to the index.

The BOJ said the maximum amount of each ETF purchase will take into account the total market value of ETFs and coverage of the indexes the ETF tracks.