The U.S. Federal Reserve's much criticized bond buying spree had only mild side-effects on other economies but the process of tightening monetary policy eventually may reverberate more harshly, an IMF report said on Monday.

The end of the Fed's second round of quantitative easing, referred to as QE2 and aimed at boosting a tepid recovery, was widely anticipated and caused no market ripples, the International Monetary Fund said in a report on the "spillover" effects of developments in the world's largest economy.

"With QE2 having limited spillovers, its fully anticipated ending will have even less effects," the IMF said in a report on how the U.S. economy affects other economies around the world. The international monetary agency is issuing similar reports for other major global economies.

Recent U.S. monetary policy has been sharply criticized, in particular by many in emerging markets, for fueling a surge of money into fast-growing economies as investors seek higher returns.

QE2 ended in June and Fed officials have said their next policy step will depend on whether a weak recovery gains strength.

The IMF said the principal risk to other economies from U.S. monetary policy comes from the eventual tightening of financial conditions, which could cause an outflow of capital from emerging markets. Higher yields on Treasury securities would also be likely, the international agency said.

The Fed cut rates to near zero in December 2008 and then launched two rounds of quantitative easing in which the central bank bought a total of $2.3 trillion in bonds to pull the U.S. economy out of a sharp recession.

The Fed's announced $600 billion in bond purchases under QE2 provoked an outcry internationally and domestically as critics argued it was driving up commodity prices and unleashing a potentially destabilizing flood of capital into emerging markets.

U.S. officials defended the buying spree, saying rising demand for commodities in large economies like China was also to blame for price rises.