"Currently the world economy stands at a very dangerous juncture," Lagarde told a roundtable on Africa's economic future in the Nigerian city of Lagos.
She said the IMF's revised global growth forecast expected in January looked to be lower than the previous one in September, which was four percent, already down from June's outlook. "And what's more, there are downside risks on the horizon that are really threatening the recovery process that had started" after the 2008-09 global financial crisis, she said.
The IMF has said Europe's worsening economy and financial market turmoil meant it will revise downwards its predictions for global growth contained in its World Economic Outlook report published three months ago.
Early this month, the UN cut its 2012 world growth forecast to 2.6 percent from 3.6 percent, warning that the global economy is "teetering on the brink of a major downturn". Lagarde said on Monday during meetings with Nigerian officials that the European debt crisis posed a risk for "all economies of the world".
She said during the roundtable in Lagos that European leaders "have made some very strong decisions" but added later that "it's going to boil down to implementation".