Up to 50,000 civilians remain trapped in the Syrian jihadist stronghold of Raqa, the UN said today, warning that supplies of water and other essentials were fast running out.
US-backed forces have been closing in on the last redoubt in Syria of the Islamic State group after penetrating its Old City last week, but an estimated 2,500 jihadists are still defending the centre.
"The UN estimates that between 30,000 and 50,000 people remain trapped in Raqa city," UN Refugee Agency (UNHCR) spokesman Andrej Mahecic said in Geneva, down from some 100,000 people at the end of June.
Mahecic stressed it was hard to be sure about the numbers given the lack of access to Raqa for UN agencies.
But he said: "Availability of food, water, medicine, electricity and other essentials has been dwindling, with the situation rapidly deteriorating.
"It is imperative that trapped civilians are able to secure safe passage out - to reach safety, shelter and protection."
IS overran Raqa in early 2014, turning the northern city into the de facto Syrian capital of their so-called "caliphate".
With help from a US-led coalition, an alliance of Kurdish and Arab fighters called the Syrian Democratic Forces is waging a fierce assault to oust IS from the city.
Raqa has been without steady running water for several weeks after damage to pipelines by heavy bombardment, including suspected strikes by the US-led coalition.
Civilians dehydrated by the blistering summer heat have been venturing out to the Euphrates river and makeshift wells around the city, risking their lives as the fighting intensifies.
Activists say they have documented symptoms of water- borne diseases among those who are drinking the river water, including fever and loss of consciousness that it is feared could indicate cholera.
The UNHCR spokesman said the agency had managed to complete a first series of humanitarian convoys by road from the province around Raqa to Qamishli in Syria's northeast.
The road had been shut by fighting for nearly two years, forcing UN agencies to use costly airlifts to reach some of the 430,000 people displaced by fighting around Raqa.
Four convoys, totalling 22 trucks, have over the past fortnight transported tents, blankets, jerry cans and other essentials to refugees who have reached Qamishli from Raqa, Mahecic said.