Yen jumped to a fresh three-week high against the dollar while the Nikkei index gave up heavy losses as investors doubt the latest government stimulus will prop up the morbid economy as world's growth slows down.

Yen last traded at 101.67 against the dollar, up a healthy 0.73% on the day, and after hitting a three-week high at 101.47, while Japan's Nikkei tumbles 244 points, or 1.47% to 16,391.

The dollar index, which tracks the greenback's performance against an array of six major counterparts, slid 0.41% to 95.36, almost touching a new three-week trough, while giving up 0.35% against the euro to 1.1202.

Crude prices tries to recover some of their recent hefty losses, with Brent futures up a meager 13 cents, or 0.31% to $42.27 a barrel, while U.S. crude futures added just seven cents, or 0.16% to $40.12 a barrel.

Investors await a basket of U.S. data later today, with personal spending expected to have risen 0.3% m/m in June, slowing down from May's 0.4% rise.

U.S. personal income on the other hand is forecast to have risen 0.3% m/m in June, accelerating from May's 0.2% rise, which would present a mixed bag for the greenback.