By Agence France-Presse
Tokyo's key Nikkei index closed marginally higher, edging up 0.04 percent after the BoJ announced it had revised down inflation forecasts while making minor changes to its ultra-loose monetary policy for the first time in nearly two years.
There had been widespread speculation in the run-up to the central bank's two-day meeting that it would alter the policy, seeking to offset the effects of negative interest rates and its massive bond and asset buying.
But the BoJ made only small adjustments by introducing some flexibility, a move that left investors relieved as it was "largely within market expectations", Hiroaki Hiwata, strategist at Toyo Securities, told AFP.
The decision sent the yen into fluctuation, with the dollar shooting up against the Japanese currency, trading at 111.31 yen against the dollar against 111.00 yen in New York.
"All eyes are on a news conference by BoJ governor (Haruhiko) Kuroda as the market wants to see how he will refer to the side effects" of the ultra-loose policy, said Masakazu Satou, senior analyst at Gaiame Online.
China's benchmark Shanghai Composite Index gained 0.3 percent by the end of trade, paring earlier losses, while July factory activity growth fell short of expectations.
Singapore was 0.3 percent up and Taipei also edged up 0.2 percent, but Hong Kong was down 0.5 percent following a negative lead on Wall Street.
US tech equities suffered a significant tumble on Monday, pushing the tech-rich Nasdaq Composite Index in New York down 1.4 percent -- the third straight day it had lost at least one percent.
Silicon Valley shares have been in retreat since Facebook last week signalled slower growth as it spends more on data security in response to criticism over its privacy policies.
The slump affecting the sector's biggest five stocks -- Facebook, Apple, Amazon, Netflix and Google -- has injected trepidation into world markets ahead of an Apple earnings announcement later Tuesday, analysts said.
"The markets heavyweight champions are having a rough day, but US markets pruned much of their losses as bank stocks and surging oil prices boosted producers," said Stephen Innes, head of Asia Pacific currency trading at OANDA.
"All eyes will remain on Nasdaq as the Wall Street wall of worry continues to build around the tech sector," he added.
Manila fell 1.3 percent, while Singapore put on 0.3 percent and Australia and Seoul were flat, as investors wait for policy announcements from the US Federal Reserve on Wednesday and the Bank of England on Thursday.
Oil prices eased in Asian trade Tuesday as concerns about oversupply sparked by rising output from key producers weighed down on market sentiment.
Prices had closed higher on Monday, driven by robust growth in the US economy -- the biggest in the world -- and a rebel attack on Saudi oil tankers in the Red Sea that forced the Saudi government to suspend crude supplies from being shipped on a key waterway.
"Crude oil prices rises as markets remain exuberant from robust US economic releases and the potential of vigorous oil demand growth," said Benjamin Lu, a commodities analyst with Phillip Futures in Singapore.
Key figures at 0730 GMT
Tokyo - Nikkei 225: UP 0.04 percent at 22,553.72 (close)
Hong Kong - Hang Seng: DOWN 0.5 percent at 28,600.51
Shanghai - Composite: DOWN 0.03 percent at 2,846.40 (close)
Euro/dollar: UP at 1.1729 from $1.1707 at 0230 GMT
Pound/dollar: UP at 1.3142 from $1.3121
Dollar/yen: UP at 111.31 from 111.01
Oil - Brent Crude: UP $1.00 at $70.46 a barrel
Oil - West Texas Intermediate: DOWN 39 cents at $74.68 a barrel
New York - Dow Jones: DOWN 0.6 percent to 25,306.83 (close)
New York - S&P 500: DOWN 0.6 percent at 2,802.60 (close)