International Monetary Fund (IMF) head Lagarde on Wednesday stated that the global financial institution cannot bend its rules when it comes to Greece, striking a somber tone in commenting on the "acute crisis" in the eurozone country.

"The IMF has been adopting a line of not silence, but we try to be mindful of developments and not be excessive in our positions," IMF Managing Director Christine Lagarde said at the Brookings Institution think-tank in Washington, D.C.

"Greece is in a situation of acute crisis, which needs to be addressed seriously and promptly," she said, adding that the IMF would be "fully engaged" in helping to find a solution.

Greece, despite being a developed country, has been fighting with deep-rooted economic crisis. In the last week's referendum, Greeks rejected European Union's bailout program.