 "People cross a busy junction outside the nightlife district in Shinjuku in Tokyo")
MSCI's broadest index of Asia-Pacific shares outside Japan erased early gains and fell 0.5 percent, taking its cue from slumping Chinese shares. The Shanghai Composite Index was down 2.4 percent and the CSI300 index was 2.6 percent lower.
Japan's Nikkei stock index was up 0.2 percent in early afternoon trading, sharply paring its morning gains. It was up 1.3 percent in the morning session, ahead of the conclusion of Bank of Japan's two-day policy meeting at which the central bank held policy steady as many had expected.
But the BOJ also warned that slowing demand in emerging markets was taking a toll on Japan's exports and output.
"There was not a strong expectation for BOJ action, but there was a market reaction after the announcement, showing some were positioning for it," said Ayako Sera, senior market economist at Sumitomo Mitsui Trust Bank in Tokyo.
"The BOJ could have decided to wait to see what the FOMC does this week, before taking any steps of its own," she said.
Later on Tuesday, investors will listen to BOJ Governor Haruhiko Kuroda's post-meeting speech for future policy clues.
The Japanese yen turned higher after the BOJ outcome, with the dollar trading at 120.04 yen, down about 0.2 percent from late U.S. trade.
The euro gave up about 0.1 percent to 135.93 yen, while it inched up about 0.1 percent to $1.1327.
The dollar index, which tracks the greenback against a basket of six major rivals, slipped about 0.1 percent to 95.186, moving back toward a three-week low of 94.913 touched overnight.
Wall Street began the week with losses, with U.S. trading volume at its lowest in a month as markets awaited the conclusion of the Fed's two-day meeting on Thursday.
Many economists believe that volatile global markets and increasing evidence of slowing momentum in China will prevent the U.S. central bank from raising interest rates for the first time since 2006.
A Reuters poll of 72 economists last week showed a slight majority expect an interest rate rise from the current 0-0.25 percent, but a smaller sample saw just a 50-50 chance.
In commodities, crude oil futures clawed back some ground lost in the previous session.
U.S. crude rose about 0.4 percent to $44.16 a barrel, underpinned by data showing a drop in U.S. supplies. It shed 1.4 percent on Monday.
Brent crude saw its early gains unravel, shedding about 0.2 percent to $46.28, after it dropped 3.7 percent on Monday to its lowest settlement in two weeks.
Spot gold edged down about 0.1 percent to $1,106.73 an ounce.
