Japan shares whipsawed and the yen surged after the Bank of Japan threw markets a smaller-than-expected bone in a keenly watched decision on Friday.
While the BOJ eased its monetary policy further by increasing its purchases of exchange-traded funds (ETFs), it didn't change interest rates or increase the monetary base, as analysts had widely expected.
The central bank said it would increase its ETF purchases so that their amount outstanding on its balance sheet would rise at an annual pace of 6 trillion yen ($56.7 billion), from 3.3 trillion yen previously.
"The message the BOJ is sending is not so much much 'whatever it takes' as 'monetary policy's pretty much played out'," said Kit Juckes, global fixed income strategist at Societe Generale.
The Japanese yen surged against the dollar after the announcement, with the dollar-yen pair falling as low as 102.85, compared with around 103.75 immediately before the decision. The pair was already volatile before the announcement, touching a session high of 105.33.
At 2:31 p.m. HK/SIN, the dollar was fetching 103.52 yen.
The benchmark Nikkei 225 whipsawed after the decision, tumbling as much as 1.66 percent immediately after the announcement. It quickly retraced the fall, but then spent the remainder of the session volleying between gains and losses. At market close, the Nikkei finished up 92.43 points, or 0.56 percent, at 16,569.27.
In the bond market, Japanese government bonds (JGBs) sold off. The yield on the benchmark 10-year JGB jumped to negative 0.169, from an earlier low of negative 0.276. Yields move inversely to bond prices. Many analysts had expected the BOJ would increase its JGB purchases.
Sean Darby, chief global equity strategist at Jefferies, said in a note that the news on the ETF purchases "should boost sentiment on stocks," but "overall monetary policy will only be marginally changed given that the BOJ's balance sheet expansion has already decelerated."
"The absence of any change on deposit rates will have disappointed those investors seeking a bolder move by the BOJ," said Darby.
Other Asian markets were nearly flat or mostly lower. The ASX 200 in Australia saw a slight gain of 5.80 points, or 0.1 percent, to 5,562.35. In South Korea, the Kospi closed down 4.91 points, or 0.24 percent, at 2,016.19. Hong Kong's Hang Seng index slipped 327.06 points, or 1.47 percent, to 21,847.28.
Chinese mainland markets were lower, with the Shanghai composite closing down 14.94 points, or 0.5 percent, at 2,979.37, while the Shenzhen composite was off by 9.44 points, or 0.48 percent, at 1,941.55.