"We have been stopped by district authorities from providing medical care," said Hans van de Weerd, India director for the group, also known by its French name Medecins sans Frontieres (MSF), in New Delhi on Saturday.

The humanitarian aid group had been providing health services to thousands of people in government-run relief camps and in villages in Chhattisgarh state's southern Dantewada district for the last year.

But questions began to be raised about the group's work some three weeks ago, escalating this week, van de Weerd said.

"On Wednesday, the district official made allegations that the reason for that is that we are supporting Naxalites," he told AFP.

"We of course deny that in the strongest form. It goes completely against our principles."

The state is the worst-affected of the 14 of India's 29 states where Maoist rebels, known locally as Naxalites, are waging an insurgency.

The accusations against the group were also carried in local news reports Saturday.

"The administration has constantly been receiving information about MSF's volunteers providing treatment to the injured and ailing Maoist cadres," Dantewada official Krishna Ram Pisda told the Times of India.

But officials, including Pisda, denied making the accusations when contacted by AFP, citing other reasons for halting MSF's work, including the security of aid workers, the lack of needed paperwork and heavy rainfall.

"It has rained heavily and the areas away from roads are flooded," said the state's most senior bureaucrat Shivraj Singh in capital Raipur, praising the group's work.

"In such a situation the security problems are there. I think they were advised: 'If you can, limit your activities to roadside villages'."

For the mean time, the health group says it is not providing any health services.

"It is a very sensitive area, where the conflict is very raw. When these accusations were being made publicly we feared for the security of our staff," said van de Weerd.