Doctors, nurses and ambulance staff from Greece's state-run hospitals and health centers have started a 24-hour strike protesting understaffing and underfunding and demanding back pay amid Greece's financial crisis.

Hospitals were functioning with emergency staff Wednesday, while a demonstration was planned for later in the day outside the health ministry.

The state hospital workers' union said Greece's national health service is "out of control due to underfunding and understaffing." It said the course of the country's negotiations with its creditors is not creating "the requirements to solve accumulated problems, and the situation is heading to a non-manageable level."

Greece's new government has been struggling to agree on reforms that creditors require in return for funds from the country's bailout needed to avoid defaulting on debts due next month.