Hong Kong's Hang Seng Index opens 3.7% lower.
Citigroup may sell off parts, or whole of firm.
New Zealand's NZX 50 index loses 2.7% to 2,573.93 in opening.
Australia's S&P/ASX 200 sheds 3.1% to 3,247.90 in opening.
Japan's Topix index falls 1.3% to 771.83 in opening.
Japan's Nikkei drops 1.3% to 7,600.35 .
