The fight to recapture the Syrian city of Raqqa, the de facto capital of IS, has entered its final stage.
But as victory looms closer for the US-led coalition, fighting alongside the Syrian Democratic Forces, there are calls to back down.
The UN's Humanitarian Advisor on Syria, Jan Egeland, is urging coalition forces to suspend their assault on the city to spare the lives thousands of trapped civilians.
"They need to do whatever is possible to make it possible for people to escape Raqqa. People that come out cannot risk air raids when they come and where they come. Now is the time to think of possibilities, pauses or otherwise, that might facilitate the escape of civilians."
The fighting means those trapped in the city are increasingly coming under attack from all sides.
The UN has accused IS and others of using civilians as human shields, and Syrian opposition sources say a number of casualties have been caused by coalition air strikes.
Mr Egeland says the situation is dire.
"The casualties, civilian casualties, are large and there seems to be no real escape for these civilians. I cannot think of a worst place on earth now than in these five neighbourhoods and for these 20,000 people."
The US-led coalition acknowledges it has escalated attacks, saying this week alone around 250 airstrikes have hit Raqqa.
It says it is "logical to assume" there has been some increase in civilian casualties, but there's no hard information backing the claims.
But it has assured all possible precautions will be taken to prevent more civilian deaths.
Survivors and witnesses have told human rights group, Amnesty International, about the situation on the ground in Raqqa.
A report details how hundreds of civilians have been killed and injured since the Raqqa offensive began in June.
Donatella Rovera, Amnesty International's Senior Crisis Response Adviser, led the investigation.
"ISIS fighters are mining and booby-trapping the escape routes, are shooting at civilians who are trying to flee, and at the same people are under a barrage of artillery and airstrikes, which are being launched by the US-led coalition forces, who are working in partnership with the local Kurdish-led militias."
The UN is hoping for a "direct negotiation" between the government and a yet-to-be-formed, unified Syrian opposition in October or November.
Talks between three disparate Syrian opposition groups were held this week in Saudi Arabia.
Ramzy Ezzeldin Ramzy, the UN deputy special envoy for Syria, says while there was some progress, the outcome of the meeting is still being assessed.
"It is important because based on our assessment of what has happened in Riyadh, we will decide as to how to move ahead in the future."
