The Nikkei slides despite data showing fall in Japanese unemployment.
The Nikkei posted its biggest one-day gain in three weeks amid a weakening of the yen.
Traders appeared to be nervous as Janet Yellen is expected to provide a hint on interest rate increase.
Yellen is expected to provide clues about the US central bank's next move on interest rates.
US new-home sales in July increased to their highest levels in nearly eight years.
Investors expect Yellen to give a hint about the timeline of the next rate increase in her speech.
Investors expect Fed chair Janet Yellen to hint at an increase in US interest rates.
NDA latest to group to attack Nigeria, due to perceived marginalisation in the area.
Oil futures remained in bull territory despite the current rally showing signs of petering out
Investors are now said to be looking forward to clarity from US Fed chairperson Janet Yellen on interest rate increase.
Oil producer lifts full-year production target by 4% and expects to reap benefits from weak sterling.
US Fed officials split on the timing of future rate increase.
New York Fed President William Dudley says the US central bank could raise interest rates as early as September.
Japan's Nikkei sees the sharpest fall following increase in the value of yen.
Aberdeen-based company expects 20% drop in full-year earnings.
Commodity giant posts weakest underlying profit in its history after reporting an 81% year-on-year drop.
China's fixed-asset investment in the year to July grew at the slowest rate in more than 16 years.
Singapore has reduced its 2016 economic growth forecast amid Brexit and weakening global demand.
US nonfarm productivity declined at a 0.5% annual rate in the second quarter ending 30 June.
China inflation numbers indicate there is room for further policy easing in the Asian country.
Oil and gas services firm reports 6% revenue increase in the first half of 2016.
Asian markets bullish despite data showing fall in China's July exports.