The sound of gunfire in the Syrian city of Aleppo.
Anti-government rebels have controlled Aleppo's east for much of the past four years, but they now look to be facing defeat having lost more than 90 per cent of the territory they once held.
Opposition activist Abdel Razak Zaqzooq.
"There is a massive displacement on the way to the besieged areas. People fled because the regime government is advancing there."
The United Nations says it is alarmed by the unverified reports of atrocities in eastern Aleppo.
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Stephen O'Brien is the UN's Under Secretary-General for Humanitarian Affairs.
"We are getting terrible, terrible reports that some young men, even as young as teenagers, and even as old as up to in their forties, are also being either subject to executions or being taken to one side. This is of grave concern."
In western Aleppo, which is under the control of the Syrian government, the war sounds like this.
Jubilant scenes as people celebrate the reports President Bashar Al Assad's forces, backed by Russia, are on the brink of victory in eastern Aleppo.
"I am happy very much, may God salute the army and may God triumph the Syrian Arab Army and thanks for every honourable citizen. May God salute the army and thank you very much."
Speaking in Paris after a meeting with the French president, the coordinator of the Syrian opposition High Negotiations Committee, Riad Hijab, says the reported gains in eastern Aleppo won't influence his group's aims.
"If Assad and his allies think that a military advance in certain quarters of Aleppo signifies that we will make concessions, or that we will make concessions on the goals of the revolution, then I say that will not happen. Not at all."
Russia's Foreign Minister Sergei Lavrov says the United States reneged on an agreement over the opening of corridors for the pull-out of fighters and civilians from east Aleppo.
"That's our position. Our American colleagues do, so to speak, agree with that, and on December 2 when we had a meeting with John Kerry in Rome they supported that very concept and even gave us their thoughts on paper. But after four days they revoked that agreement and returned to their old and, as I see it, dead end position which stipulates that before agreeing on any corridors a pause should be announced for the duration of three, four or seven days. But as you understand, we have already been through this. This would mean that the militants would yet again be given a break."
The United States says nothing less than an immediate ceasefire was required because of the continued attacks on civilians.
The British-based Syrian Observatory for Human Rights says at least 415 civilians and 364 rebel fighters have been killed in eastern Aleppo since November 15 and another 130 civilians have died in rocket and mortar attacks in the government-controlled west.
