Summary executions and forced conscription: 'A complete meltdown of humanity' is underway in Aleppo

Pro-government forces in Syria are on the brink of completely recapturing the city of Aleppo from opposition forces, after a month of intense bombing accompanied by a ferocious ground offensive that has forced rebels and civilians into hiding.

Talks between Russia - an ally of Syrian President Bashar al-Assad - and members of the opposition, aimed at establishing a ceasefire and evacuating civilians from the city, are currently being mediated by Turkish officials in Ankara.

As of Tuesday morning, an early agreement had been made to evacuate about 40,000 people from the city, a source within the opposition with knowledge of the talks told Business Insider.

The preliminary agreement came amid reports that pro-government forces, including regime troops and Shiite militias backed by Iran - another Assad ally - had summarily executed dozens of civilians, including women and children, as they moved to clear rebel-held areas.

Many of the civilians executed by pro-government forces were injured and awaiting treatment in the city's makeshift medical facilities, reports from the scene said. Others were trying to flee their homes when they were executed.

It's "a complete meltdown of humanity," United Nations humanitarian spokesman Jens Laerke said.

The government forces also set fire to a building used to house people who had been displaced in the fighting, with as possibly more than 100 children trapped inside.

"According to alarming reports from a doctor in the city, many children, possibly more than 100, unaccompanied or separated from their families, are trapped in a building, under heavy attack in east Aleppo," Unicef said in a statement. "We urge all parties to the conflict to allow the safe and immediate evacuation of all children."

Employees at the underground Hayat Medical Center in Aleppo, run by the Syrian American Medical Society (SAMS), were also executed by pro-government forces on Monday, said Mouaz Moustafa, the executive director of the Syrian Emergency Task Force.

"They literally executed each staff member," Moustafa, a prominent activist from Damascus now living in Washington, DC, told Business Insider.

Assad's forces are also using forced conscription to take over and clear areas of the besieged half of the city. Images circulated by pro-government sources on Monday showed Syrian men and boys from east Aleppo standing in front of government forces inside a detention camp.

An estimated 100,000 people are still trapped in a "hellish corner" of less than one mile of territory in eastern Aleppo that hasn't yet fallen to government forces, said Rupert Colville, a spokesman for the United Nations' human rights office. He said in a press conference that the UN had received reports of pro-government forces killing least 82 civilians, including 11 women and 13 children, in four different neighborhoods.

Civilians trying to flee their homes were also being shot in the street by pro-Assad forces, said Laerke, the UN humanitarian spokesman.

As neighborhoods fall, one by one, to regime troops, there has been a concentration of bombing and "horrendous war crimes" being perpetrated against civilians, Moustafa said.

"And it's all being done with Russian aerial cover, including cluster bombs and barrel bombs," he said.

He said he had received reports that the regime was also using chemical weapons, such as chlorine and white phosphorous, to clear the rebel-held areas. Those reports are unconfirmed.

"Why should I lie? I'm not well," Malek, an activist inside Aleppo, told the New York Times. "We are people, are being deleted from the human map. We have two neighborhoods and one street, and the regime will keep bombing this small area."

The US has been shut out of the new round of negotiations hosted in Ankara, two sources close to the opposition have told Business Insider.

The talks were initially aimed at securing a deal to deliver humanitarian aid to eastern Aleppo in exchange for the evacuation of extremists groups like the former Al Qaeda affiliate Jabhat Fateh al-Sham. Separate negotiations between Russia and the US were apparently underway simultaneously to evacuate rebel groups from Aleppo, allowing civilians to stay and receive humanitarian aid.

The rebels proposed instead that civilians be evacuated from the city, and they are not making preparations to evacuate.

"The rebels are holding and fighting, knowing they face certain death," Moustafa said.

Syria's chief opposition coordinator, Riad Hijab, said on Monday that the rebels "will not make any concessions."

"If Assad and his allies think that a military advance in certain quarters of Aleppo will signify that we will make concessions, then (I say) that will not happen," Hijab told reporters in Paris after meeting with French president Francois Hollande. "We will not make any concessions."