AMMAN (Reuters) - Disruption of fuel supplies due to fighting between rebel groups in northern Syria is threatening the closure of hospitals and paralysing the work of ambulances and rescue services, an international medical charity said on Sunday.

Islamic State militants have closed a checkpoint under their control in the countryside north of the city of Aleppo to trucks carrying fuel to areas in northern Syria held by other rebel groups.

Medecins Sans Frontieres said in a statement obtained by Reuters and to be released later that it had received distress calls from health centres in rebel-held areas in Aleppo, Idlib and Hama provinces to say they were running out of fuel needed to run life-saving equipment.

"With so many hospitals now at a risk of closure, the lives of many Syrians are in even greater danger," said Dounia Dekhili, MSF Programme Manager for Syria, where the charity conducts an extensive humanitarian operation.

"Fuel is needed to run water pumps for clean water, to run incubators for newborns and to run ambulances for lifesaving care," she said.

Work by civil defence workers who were helping rescue survivors of air bombardments in rebel-held areas could be halted if the shortages continue, MSF said.

Islamic State militants, seeking to choke off fuel supplies heading to its rivals battling for control of the area, had almost completely barred oil truckers from passing through the gateway of Tel Qarah.

The checkpoint, near the Turkish border, separates territory run by Islamic State fighters and their rivals, residents and traders in the area said.

Hundreds of private trucks used to pass through the crossing daily, carrying crudely processed oil bought from fields under the control of Islamic State in eastern Syria, to sell to the rest of northern rebel-held Syria.

It was the major source of fuel for those areas largely cut off from supplies from President Bashar al Assad's government.

Rebels from a coalition of Western backed and Islamist groups fighting to beat off the Islamic State offensive said the closure was causing severe hardship to civilians.

The fuel shortages began to bite almost a week ago and have pushed prices of diesel needed to run electricity generators, bakeries and hospitals. A litre of diesel now cost two dollars, up from less than half a dollar, residents said.

(Reporting by Suleiman Al-Khalidi; Editing by Rosalind Russell)