International Monetary Fund chief Christine Lagarde on Thursday hailed the European Central Bank's decision to launch a massive stimulus program, but urged eurozone authorities to undertake needed economic reforms.

"The planned expansion of the ECB's balance sheet will help lower borrowing cost across the euro area, raise inflation expectations and reduce the risk of a protracted period of low inflation," the IMF managing director said in a statement.

"These measures will also strongly increase the prospects of the ECB achieving its price stability mandate."

However, she added, "It remains essential that the accommodative monetary stance is supported by comprehensive and timely policy actions in other areas, not least structural reforms to boost potential growth and ensure broad political support for demand management policies."

The comments came after the ECB announced a 60 billion euro ($69 billion) per month program to purchase public and private debt to ward off the risk of deflation.

The quantitative easing program will begin in March and continue through at least September 2016, the central bank said, in a bid to lift low inflation toward its target of just below 2.0 percent.

The IMF for several months has been urging the ECB to do more to boost lagging growth in the 19-nation eurozone, a main source of the slowdown in the global economy. (AFP)