Shares of U.S. tech giants, including Facebook, Netflix and Google parent Alphabet, all declined overnight in the first trading session of the month, having first sold off in March.
E-commerce giant Amazon, one of the best performers over the past year, declined after U.S. President Donald Trump criticized the company in a series of tweets.
Investors also digested China's announcement that it is imposing tariffs on 128 kinds of U.S. products, beginning Monday, in response to U.S. duties on steel and aluminum imports unveiled last month. Beijing said in March that those products had an import value of $3 billion in 2017.
Analysts saw the move as largely measured, although there was concern that retaliation from U.S. trading partners would be negative for global economic growth.
In corporate news, Australian oil and gas company Santos announced Tuesday that it had received a $10.4 billion takeover proposal from Harbour Energy, Reuters said.
Meanwhile, South Korea's SK Innovation was down 2.34 percent in early trade. Reuters reported that the company said on Monday it intended to sell shares in its SK Lubricants unit as part of a planned initial public offering.
The dollar index, which tracks the U.S. currency against six peers, stood at 90.065 by 8:04 a.m. HK/SIN.
Against the yen, the dollar extended losses, slipping below the 106 level to trade at 105.73. Monday marked the third consecutive session the greenback slid against the safe-haven Japanese currency.