The IMF, a Washington-based crisis lender, has now issued nearly 11 billion dollars to recession-plagued Greece as part of a bailout agreement.
"The Greek authorities have continued to make commendable progress in reducing fiscal and external imbalances," IMF chief Christine Lagarde said.
"However, progress on institutional and structural reforms, in the public sector and beyond, has still not been commensurate with the problems facing Greece. Greater reform efforts remain key to an economic recovery and lasting growth."
The European Union on Friday said Athens had met all the conditions to receive 5.3 billion dollars from the eurozone's rescue fund and from a separate central bank programme involving the purchase of Greek bonds.
The Greek Parliament passed measures this month to reduce the government payroll.
Lagarde said that Greece must still do more to improve revenue collection and combat tax evasion, and push structural reforms that can increase long-term growth prospects.