File photo: AFP

Japanese markets swung wildly on Monday after the Bank of Japan announced emergency monetary policy measures, initially jumping before trimming gains as investors tried to digest the moves.

The benchmark Nikkei 225 jumped nearly two percent in the minutes after the central bank announced it would follow its counterparts around the world in an attempt to shore up sentiment as the new coronavirus outbreak raises fears of a global recession.

But Tokyo's main index was only up 0.33 percent or 57.22 points at 17,488.27 by 0530 GMT, with the broader Topix up 0.90 percent or 11.30 points at 1,273.00.

The Japanese markets had been virtually flat before the announcement from the BoJ, which brought forward a two-day meeting it was scheduled to hold from Tuesday to take emergency action.

The central bank said it would double its annual capacity to purchase exchange-traded funds and Japan real estate investment funds, the latest global central bank to take emergency action.

The BoJ said it would also introduce a new operation to provide loans against corporate debt and raised its annual limit for corporate bond purchases by one trillion yen to 4.2 trillion yen.

But it left its main interest rate unchanged at minus 0.1 percent and also kept its upper limit for purchasing government bonds at 80 trillion yen.

It warned in a statement of "significant uncertainties over the consequences of the outbreak of COVID-19."