Greece and its creditors need to "get on with the work" to implement reforms after the cash-strapped European nation met its most recent debt repayment deadline to the International Monetary Fund, Christine Lagarde, managing director of the IMF, told CNBC on Thursday.

Greece paid in full a 450 million euro ($485 million) obligation to the IMF earlier Thursday, temporarily easing concerns of a potential default. Lagarde—who met with Greek leaders on Sunday—noted that Greece and its creditors should look to identify measures to improve a "very bad economic situation" in the country.