Japan's key Nikkei 225 Stock Average fell to a four-year low on Monday on worries about the financial crisis, despite US Congressional approval of a Wall Street bail-out.
The benchmark Nikkei index was trading early afternoon (1:43 p.m.) at 10,434.17, down 503.97 points, or 4.60 per cent.
The broader Topix index of all first-section issues fell below the psychological marker of 1,000 points for the first time since December 2003.
It is the first trading day in Tokyo since the US Lower House approved on Friday, after tough negotiations, the $700-billion rescue package for the financial sector.
Meanwhile, the Japanese central bank pumped funds into the short-term money markets for the 14th consecutive trading day. On Monday, 1 trillion yen ($9.5 billion) was injected to ease strains on the financial system.
On currency markets at 9 am, the dollar was quoted at 104.52-57 yen, down from Friday's 5 pm quote of 105.01-03 yen.
The euro was quoted at $1.3650-55, down from Thursday's 5 pm quote of $1,3836-38, and at 142.68-73 yen, down from 145.30-34 yen.