A rebel-held area of Syria has been hit by an outbreak of typhoid after power cuts hit water supplies and forced the population to turn to the Euphrates River, the UN's health agency warned Tuesday.

Tarik Jasarevic, spokesman for the , told AFP that some 2,500 people had caught the disease in the country's northeast.

"They don't have access to clean water, or electricity to work their pumps, so they draw water from the river," he said.

The ability of international aid agencies to operate in Syria has been limited, despite the glaring needs created by a bloody civil war which broke out in March 2011 when the regime of President Bashar al-Assad cracked down on protests.

Access to opposition-controlled areas has been particularly difficult, as it involves crossing battle frontlines, while the Syrian government has maintained restrictions on international aid group operations.

"We're working with local groups to provide typhoid treatment," said Jasarevic.

There have been no reports of deaths so far, he said.

"But the mortality rate from typhoid can be extremely high if it is not dealt with," he warned.

is a spread by food or drink contaminated with the or urine of infected people.