The Russian rouble tumbled on Thursday, at one point losing 2% to the dollar in volatile trade and hitting a more than five-month low versus the euro as the White House announced new sanctions targeting Russia's sovereign debt.
The central bank ramped up buying of sovereign bonds after a surge in U.S. Treasury yields lifted borrowing costs in the bloc and threatened Europe's tentative recovery.
The U.S. Dollar Currency Index, which measures the greenback against a basket of six currencies, was 0.181% lower at 92.473. The index fell as low as 92.134 earlier in the session.
Once recovery starts to take hold and investors buy into risk-bearing instruments, nominal bond yields will inevitably move higher and "no amount" of ECB buying can completely undo that.