The Bank of Japan announced an expansion to its asset purchase program of 5 trillion yen, taking the total to 40 trillion yen ($486 billion), while holding its monetary policy rate unchanged at 0-0.10%. The move followed the powerful 8.9 earthquake which struck Japan on Friday, causing tsunamis and damage to nuclear power plants. Japanese stocks fell about 5% when the market opened on Monday. The Bank also said it would inject as much as 15 trillion yen ($183.8 billion) into money markets to stabilize the financial system.
Monetary Policy Announcement: http://www.boj.or.jp/en/announcements/release_2011/k110314a.pdf
Amendment to Asset Purchase Program: http://www.boj.or.jp/en/announcements/release_2011/rel110314i.pdf