The UN has expressed concern about the first confirmed cholera outbreak in Syria in years, saying it poses a "serious threat" to the entire region.

More than 900 suspected cases and eight deaths have been reported in the war-torn country in the past three weeks.

The outbreak has been concentrated in Aleppo and Deir al-Zour provinces.

It is believed to be linked to people drinking contaminated water from the River Euphrates, which flows through the provinces, and using it on crops.

The outbreak is also seen as an indicator of the severe shortages of water throughout Syria caused by climate change and conflict.

Rising temperatures, below-average rainfall and reduced flow from upstream neighbour Turkey have resulted in critically low levels in the Euphrates.

That, combined with widespread damage to supply and sewerage infrastructure, has left many of the 5 million Syrians who depend on the river for drinking water and crop irrigation reliant on unsafe sources. It has also triggered an increase in dangerous water-borne diseases like cholera.

The Syrian health ministry said on Monday that 20 cases of cholera, including two deaths, had been confirmed by laboratories in the northern province of Aleppo, the state-run Sana news agency reported.

It added that another four cases had been confirmed in the coastal province of Latakia as well as two in the capital Damascus among patients from Aleppo.

However, the UN warned that surveillance data showed a total of 936 severe acute diarrhoea cases, including at least eight related deaths, had been recorded across Syria since 25 August.

More than 670 of those suspected cases and six of the deaths were in Aleppo, while 201 cases and two deaths were in the eastern province of Deir al-Zour.

"The outbreak presents a serious threat to people in Syria and the region," warned the UN Humanitarian Co-ordinator in Syria, Imran Riza.

"Swift and urgent action is needed to prevent further illness and death," he added, appealing to donor countries for urgent additional funding.

The UN said rapid diagnostic tests, intravenous fluids and rehydration salts had been delivered to health facilities in affected communities and other high-risk areas, such as camps for displaced people. Clean water is also being delivered by lorries and chlorination is being scaled up.

Cholera is an acute diarrhoeal infection caused by ingestion of food or water contaminated with the bacterium Vibrio cholera. In severe cases, the disease can kill within hours if left untreated.