Oil prices tumbled to fresh multi-month lows alongside other commodities, while the yen surged versus its rivals after the Bank of Japan disappointed investors by less-than-expected easing measures, as it only doubled its purchases of exchange-traded funds to $58 billion, leaving every thing else the same.

U.S. crude futures tumbled for the eight session to $40.63 a barrel, with a 1.22% loss and a 3-1/2 month low at $40.58, while Brent crude futures shed 1.41% to hover around $42.62 a barrel.

The yen spiked to fresh two-week highs after BoJ's decisions, last trading at 103.68 against the dollar, up 1.50% on the day, and after touching an earlier high at 102.72.

Other commodities suffered losses alongside oil, with gold futures down nearly three dollars, or 0.21% to $1,338 an ounce, while silver futures lost nine cents, or 0.47% to hover around $20.09 an ounce. Copper gave up 0.23% to $2.204 a pound.

Investors await an array of data later, with U.S. GDP expected to have grown 2.6% annually in the second quarter, which would help the dollar regain its footing.

U.S. consumer spending is forecast to inch up in a survey to 90.2 in July from June's 89.2, which would confirm the steadiness of consumer spending and uphold the dollar as well.