With Wall Street providing a weak lead after poor earnings from aluminium giant Alcoa, investors focused on Japan after the country was jolted on Monday -- a month after the March 11 tragedy -- by a 6.6 magnitude quake.
Tokyo gave up 1.60 percent by the break, while Hong Kong fell 1.31 percent, Sydney dropped 1.19 percent and Seoul was down 1.23 percent. Shanghai shed 0.24 percent.
Monday's earthquake forced the evacuation of the Fukushima Daiichi nuclear plant after it briefly cut power to three reactors already crippled by last month's 9.0 quake and resulting tsunami.
The Fukushima crisis was again in focus after Japan upgraded its nuclear emergency to a maximum seven on an international scale, the first time the ranking has been invoked since the Chernobyl disaster in 1986.
Japan's nuclear safety watchdog said radiation emissions from the plant were equal to 10 percent of those produced by Chernobyl.
Shares in Tokyo Electric Power (TEPCO), the operator of the plant, were down more than 6 percent at 469 yen in early trade.
"There is unlikely to be any medium to long-term moves to buy Japanese stocks. Foreign investors are especially nervous," Hisatsune Kobayashi at SMBC Nikko Securities told Dow Jones Newswires.
The US earnings season got off to a weak start with Alcoa falling in after-hours trading after it reported sales growth was worse than expected.
"There is going to be more of a wait-and-see attitude as investors brace for additional US earnings, especially from financial institutions this week," said Yumi Nishimura, deputy general manager at Daiwa Securities.
The Dow Jones Industrial Average ended just 0.01 percent higher, the tech-rich Nasdaq fell 0.32 percent and the S&P 500, a broad measure of the markets, dropped 0.28 percent.
On currency markets dealers worried by the latest developments in Japan moved into safer haven units.
The dollar stood at 84.19 yen, down from 84.67 yen in New York.
The euro was at $1.4411 and 121.37 yen, off from $1.4436 and 122.10 in New York Monday.
Sentiment was also dented after the International Monetary Fund in its World Economic Outlook forecast for the global economy to expand 4.4 percent this year from 5.0 percent last year, citing rising oil prices as a major headwind.
In early Asian trade, New York's main West Texas Intermediate (WTI) futures contract, light sweet crude for delivery in May, dived $1.49 to $108.43 per barrel.
Brent North Sea crude for May delivery slipped $1.44 to $122.54.
Gold opened at $1,458.00-$1,459.00 an ounce in Hong Kong, down from Monday's close of $1,474.00-$1,475.00.